Wherever you go in Iraq's southern city of Basra, there is dust. It rolls down the long roads that are the desert's fingers. It gets in your eyes and nose and throat; it swirls in markets and school playgrounds, consuming children kicking a plastic ball; and it carries, according to Dr Jawad Al-Ali, 'the seeds of our death'...

Dr Al-Ali is a cancer specialist at Basra's hospital and a member of Britain's Royal College of Physicians. He has a neat moustache and a kindly, furrowed face. His starched white coat, like the collar of his shirt, is frayed.

"Before the Gulf War, we had only three or four deaths in a month from cancer," he said. "Now it's 30 to 35 patients dying every month, and that's just in my department. That is a 12-fold increase in cancer mortality. Our studies indicate that 40 to 48 per cent of the population in this area will get cancer: in five years' time to begin with, then long afterwards. That's almost half the population.

"Most of my own family now have cancer, and we have no history of the disease. We don't know the precise source of the contamination, because we are not allowed to get the equipment to conduct a proper survey, or even test the excess level of radiation in our bodies. We strongly suspect depleted uranium, which was used by the Americans and British in the Gulf War right across the southern battlefields. Whatever the cause, it is like Chernobyl here; the genetic effects are new to us.

"The mushrooms grow huge, and the fish in what was once a beautiful river are inedible. Even the grapes in my garden have mutated and can't be eaten."

Along the corridor, I met Dr Ginan Ghalib Hassen, a paediatrician. At another time, she might have been described as an effervescent personality; now she, too, has a melancholy expression that does not change; it is the face of Iraq. "This is Ali Raffa Asswadi," she said, stopping to take the hand of a wasted boy I guessed to be about four years old. "He is nine. He has leukaemia. Now we can't treat him. Only some of the drugs are available. We get drugs for two or three weeks, and then they stop when the shipments stop. Unless you continue a course, the treatment is useless. We can't even give blood transfusions, because there are not enough blood bags."

Dr Hassen keeps a photo album of the children she is trying to save and those she has been unable to save. "This is Talum Saleh," she said, turning to a photograph of a boy in a blue pullover and with sparkling eyes. "He is five-and-a-half years old. This is a case of Hodgkin's disease. Normally a patient with Hodgkin's can expect to live and the cure can be 95 per cent. But if the drugs are not available, complications set in, and death follows. This boy had a beautiful nature. He died."

I said, "As we were walking, I noticed you stop and put your face to the wall." "Yes, I was emotional ... I am a doctor; I am not supposed to cry, but I cry every day, because this is torture. These children could live; they could live and grow up; and when you see your son and daughter in front of you, dying, what happens to you?" I said, "What do you say to those in the West who deny the connection between depleted uranium and the deformities of these children?" "That is not true. How much proof do they want? There is every relation between congenital malformation and depleted uranium. Before 1991, we saw nothing like this at all. If there is no connection, why have these things not happened before? Most of these children have no family history of cancer.

"I have studied what happened in Hiroshima. It is almost exactly the same here; we have an increased percentage of congenital malformation, an increase of malignancy, leukaemia, brain tumours: the same."

Under the economic embargo imposed by the United Nations Security Council, now in its 14th year, Iraq is denied equipment and expertise to decontaminate its battlefields from the 1991 Gulf War.

Professor Doug Rokke, the US Army physicist responsible for cleaning up Kuwait, told me: "I am like many people in southern Iraq. I have 5,000 times the recommended level of radiation in my body. Most of my team are now dead.

"We face an issue to be confronted by people in the West, those with a sense of right and wrong: first, the decision by the US and Britain to use a weapon of mass destruction: depeleted uranium. When a tank fired its shells, each round carried over 4,500g of solid uranium. What happened in the Gulf was a form of nuclear warfare."

In 1991, a United Kingdom Atomic Eneregy Authority document reported that if 8 per cent of the depleted uranium fired in the Gulf War was inhaled, it could cause "500,000 potential deaths". In the promised attack on Iraq, the United States will again use depleted uranium, and so will Britain, regardless of its denials.

Professor Rokke says he has watched Iraqi officials pleading with American and British officials to ease the embargo, if only to allow decontaminating and cancer assessment equipment to be imported. "They described the deaths and horrific deformities, and they were rebuffed," he said. "It was pathetic."

The United Nations Sanctions Committee in New York, set up by the Security Council to administer the embargo, is dominated by the Americans, who are backed by the British. Washington has vetoed or delayed a range of vital medical equipment, chemotherapy drugs, even pain-killers. (In the jargon of denial, "blocked" equals vetoed, and "on hold" means delayed, or maybe blocked.) In Baghdad, I sat in a clinic as doctors received parents and their children, many of them grey-skinned and bald, some of them dying. After every second or third examination, Dr Lekaa Fasseh Ozeer, the young oncologist, wrote in English: "No drugs available." I asked her to jot down in my notebook a list of drugs the hospital had ordered, but had not received, or had received intermittently. She filled a page.

I had been filming in Iraq for my documentary Paying the Price: Killing the Children of Iraq. Back in London, I showed Dr Ozeer's list to Professor Karol Sikora who, as chief of the cancer programme of the World Health Organisation (WHO), wrote in the British Medical Journal: "Requested radiotherapy equipment, chemotherapy drugs and analgesics are consistently blocked by United States and British advisers [to the Sanctions Committee]. There seems to be a rather ludicrous notion that such agents could be converted into chemical and other weapons.

Nearly all these drugs are available in every British hospital. They are very standard. When I came back from Iraq last year, with a group of experts I drew up a list of 17 drugs deemed essential for cancer treatment. We informed the UN that there was no possibility of converting these drugs into chemical warfare agents. We heard nothing more.

"The saddest thing I saw in Iraq was children dying because there was no chemotherapy and no pain control. It seemed crazy they couldn't have morphine, because for everybody with cancer pain, it is the best drug. When I was there, they had a little bottle of aspirin pills to go round 200 patients in pain. They would receive a particular anti-cancer drug, but then get only little bits of drugs here and there, and so you can't have any planning. It's bizarre."

I told him that one of the doctors had been especially upset because the UN Sanctions Committee had banned nitrous oxide as "weapons dual use"; yet this was used in caesarean sections to stop bleeding, and perhaps save a mother's life. "I can see no logic to banning that," he said. "I am not an armaments expert, but the amounts used would be so small that, even if you collected all the drugs supply for the whole nation and pooled it, it is difficult to see how you could make any chemical warfare device out of it."

Denis Halliday is a courtly Irishman who spent 34 years with the UN, latterly as Assistant Secretary-General. When he resigned in 1998 as the UN's Humanitarian Co-ordinator for Iraq in protest at the effects of the embargo on the civilian population, it was, he wrote, "because the policy of economic sanctions is totally bankrupt. We are in the process of destroying an entire society. It is as simple as that ... Five thousand children are dying every month ... I don't want to administer a programme that results in figures like these."

Since I met Halliday, I have been struck by the principle behind his carefully chosen, uncompromising words. "I had been instructed," he said, "to implement a policy that satisfies the definition of genocide: a deliberate policy that has effectively killed well over a million individuals, children and adults. We all know that the regime – Saddam Hussein – is not paying the price for economic sanctions; on the contrary, he has been strengthened by them. It is the little people who are losing their children or their parents for lack of untreated water. What is clear is that the Security Council is now out of control, for its actions here undermine its own Charter, and the Declaration of Human Rights and the Geneva Convention. History will slaughter those responsible."

In the UN, Mr Halliday broke a long collective silence. On 13 February, 2000, Hans Von Sponeck, who had succeeded him as Humanitarian Co-ordinator in Baghdad, resigned. Like Halliday, he had been with the UN for more than 30 years. "How long," he asked, "should the civilian population of Iraq be exposed to such punishment for something they have never done?" Two days later, Jutta Burghardt, head of the World Food Programme in Iraq, another UN agency, resigned, saying that she, too, could no longer tolerate what was being done to the Iraqi people.

The resignations were unprecedented. All three were saying the unsayable: that the West was responsible for mass deaths, estimated by Halliday to be more than a million. While food and medicines are technically exempt, the Sanctions Committee has frequently vetoed and delayed requests for baby food, agricultural equipment, heart and cancer drugs, oxygen tents, X-ray machines. Sixteen heart and lung machines were put "on hold" because they contained computer chips. A fleet of ambulances was held up because their equipment included vacuum flasks, which keep medical supplies cold; vacuum flasks are designated "dual use" by the Sanctions Committee, meaning they could possibly be used in weapons manufacture. Cleaning materials, such as chlorine, are "dual use", as is the graphite used in pencils; as are wheelbarrows, it seems, considering the frequency of their appearance on the list of "holds".

As of October 2001, 1,010 contracts for humanitarian supplies, worth $3.85bn, were "on hold" by the Sanctions Committee. They included items related to food, health, water and sanitation, agriculture and education. This has now risen to goods worth more than $5bn. This is rarely reported in the West.

When Denis Halliday was the senior United Nations official in Iraq, a display cabinet stood in the foyer of his office. It contained a bag of wheat, some congealed cooking oil, bars of soap and a few other household necessities. "It was a pitiful sight," he said, "and it represented the monthly ration that we were allowed to spend. I added cheese to lift the protein content, but there was simply not enough money left over from the amount we were allowed to spend, which came from the revenue Iraq was allowed to make from its oil."

He describes food shipments as "an exercise in duplicity". A shipment that the Americans claim allows for 2,300 calories per person per day may well allow for only 2,000 calories, or less. "What's missing," he said, "will be animal proteins, minerals and vitamins. As most Iraqis have no other source of income, food has become a medium of exchange; it gets sold for other necessities, further lowering the calorie intake. You also have to get clothes and shoes for your kids to go to school. You've then got malnourished mothers who cannot breastfeed, and they pick up bad water.

What is needed is investment in water treatment and distribution, electric power for food processing, storage and refrigeration, education and agriculture." His successor, Hans Von Sponeck, calculates that the Oil for Food Programme allows $100 (£63) for each person to live on for a year. This figure also has to help pay for the entire society's infrastructure and essential services, such as power and water.

"It is simply not possible to live on such an amount," Mr Von Sponeck told me. "Set that pittance against the lack of clean water, the fact that electricity fails for up to 22 hours a day, and the majority of sick people cannot afford treatment, and the sheer trauma of trying to get from day to day, and you have a glimpse of the nightmare. And make no mistake, this is deliberate. I have not in the past wanted to use the word genocide, but now it is unavoidable."

The cost in lives is staggering. A study by the United Nations Children's Fund (Unicef) found that between 1991 and 1998, there were 500,000 deaths above the anticipated rate among Iraqi children under five years of age. This, on average, is 5,200 preventable under-five deaths per month.

Hans Von Sponeck said, "Some 167 Iraqi children are dying every day." Denis Halliday said, "If you include adults, the figure is now almost certainly well over a million." A melancholia shrouds people. I felt it at Baghdad's evening auctions, where intimate possessions are sold to buy food and medicines. Television sets are common. A woman with two infants watched their pushchairs go for pennies. A man who had collected doves since he was 15 came with his last bird; the cage would go next.

My film crew and I had come to pry, yet we were made welcome; or people merely deferred to our presence, as the downcast do. During three weeks in Iraq, only once was I the brunt of someone's anguish. "Why are you killing the children?" shouted a man in the street. "Why are you bombing us? What have we done to you?" Through the glass doors of the Baghdad offices of Unicef you can read the following mission statement: "Above all, survival, hope, development, respect, dignity, equality and justice for women and children."

Fortunately, the children in the street outside, with their pencil limbs and long thin faces, cannot read English, and perhaps cannot read at all. "The change in such a short time is unparalleled, in my experience," Dr Anupama Rao Singh, Unicef's senior representative in Iraq, told me.

"In 1989, the literacy rate was more than 90 per cent; parents were fined for failing to send their children to school. The phenomenon of street children was unheard of. Iraq had reached a stage where the basic indicators we use to measure the overall wellbeing of human beings, including children, were some of the best in the world. Now it is among the bottom 20 per cent."

Dr Singh, diminutive, grey-haired and, with her precision, sounding like the teacher she once was in India, has spent most of her working life with Unicef. She took me to a typical primary school in Saddam City, where Baghdad's majority and poorest live. We approached along a flooded street, the city's drainage and water distribution system having collapsed since the Gulf War bombing. The headmaster, Ali Hassoon, guided us around the puddles of raw sewage in the playground and pointed to the high-water mark on the wall. "In the winter it comes up to here. That's when we evacuate.

We stay for as long as possible but, without desks, the children have to sit on bricks. I am worried about the buildings coming down." As we talked, an air-raid siren sounded in the distance.The school is on the edge of a vast industrial cemetery. The pumps in the sewage treatment plants and the reservoirs of potable water are silent, save for a few wheezing at a fraction of their capacity. Those that were not bombed have since disintegrated; spare parts from their British, French and German manufacturers are permanently "on hold".

Before 1991, Baghdad"s water was as safe as any in the developed world. Today, drawn untreated from the Tigris, it is lethal. Just before Christmas 1999, the Department of Trade and Industry in London restricted the export of vaccines meant to protect Iraqi children against diphtheria and yellow fever.

Dr Kim Howells told Parliament why. His title of Parliamentary Under Secretary of State for Competition and Consumer Affairs perfectly suited his Orwellian reply. The children's vaccines were, he said, "capable of being used in weapons of mass destruction".

American and British aircraft operate over Iraq in what their governments have unilaterally declared "no fly zones". This means that only they and their allies can fly there. The designated areas are in the north, around Mosul, to the border with Turkey, and from just south of Baghdad to the Kuwaiti border. The US and British governments insist the no fly zones are "legal", claiming that they are part of, or supported by, the Security Council's Resolution 688.

There is a great deal of fog about this, the kind generated by the Foreign Office when its statements are challenged. There is no reference to no fly zones in Security Council resolutions, which suggests they have no basis in international law.

I went to Paris and asked Dr Boutros Boutros-Ghali, the Secretary-General of the UN in 1992, when the resolution was passed. "The issue of no fly zones was not raised and therefore not debated: not a word," he said. "They offer no legitimacy to countries sending their aircraft to attack Iraq." "Does that mean they are illegal?" I asked. "They are illegal," he replied.

The scale of the bombing in the no fly zones is astonishing. Between July 1998 and January 2000, American air force and naval aircraft flew 36,000 sorties over Iraq, including 24,000 combat missions. In 1999 alone, American and British aircraft dropped more than 1,800 bombs and hit 450 targets. The cost to British taxpayers is more than £800m.

There is bombing almost every day: it is the longest Anglo-American aerial campaign since the Second World War; yet it is mostly ignored by the British and American media. In a rare acknowledgement, The New York Times reported, "American warplanes have methodically and with virtually no public discussion been attacking Iraq ... pilots have flown about two-thirds as many missions as Nato pilots flew over Yugoslavia in 78 days of around-the-clock war there."

The purpose of the no fly zones, according to the British and American governments, is to protect the Kurds in the north and the Shi'a in the south against Saddam Hussein's forces. The aircraft are performing a "vital humanitarian task", says Tony Blair, that will give "minority peoples the hope of freedom and the right to determine their own destinies".

Like much of Blair's rhetoric on Iraq, it is simply false. In nothern Kurdish Iraq, I interviewed members of a family who had lost their grandfather, their father and four brothers and sisters when a "coalition" aircraft dive-bombed them and the sheep they were tending. The attack was investigated and verified by Hans Von Sponeck who drove there especially from Baghdad. Dozens of similar attacks – on shepherds, farmers, fishermen – are described in a document prepared by the UN Security Section.

The US faced a "genuine dilemma" in Iraq, reported The Wall Street Journal. "After eight years of enforcing a no fly zone in ... Iraq, few military targets remain. 'We're down to the last outhouse,' one US official protested. 'There are still some things left, but not many.'"

There are still children left. Six children died when an American missile hit Al Jumohria, a community in Basra's poorest residential area: 63 people were injured, a number of them badly burned. "Collateral damage," said the Pentagon. I walked down the street where the missile had struck in the early hours; it had followed the line of houses, destroying one after the other. I met the father of two sisters, aged eight and 10, who were photographed by a local wedding photographer shortly after the attack. They are in their nightdresses, one with a bow in her hair, their bodies entombed in the rubble of their homes, where they had been bombed to death in their beds. These images haunt me.

I flew on to New York for an interview with Kofi Annan, the Secretary-General of the United Nations. He appears an oddly diffident man, so softly spoken as to be almost inaudible.

"As the Secretary-General of the United Nations which is imposing this blockade on Iraq," I said, "what do you say to the parents of the children who are dying?" His reply was that the Security Council was considering "smart sanctions", which would "target the leaders" rather than act as "a blunt instrument that impacts on children". I said the UN was set up to help people, not harm them, and he replied, "Please do not judge us by what has happened in Iraq."

I walked to the office of Peter van Walsum, the Netherlands' ambassador to the UN and the chairman of the Sanctions Committee. What impressed me about this diplomat with life-and-death powers over 22 million people half a world away was

that, like liberal politicians in the West, he seemed to hold two diametrically opposed thoughts in his mind. On the one hand, he spoke of Iraq as if everybody were Saddam Hussein; on the other, he seemed to believe that most Iraqis were victims, held hostage to the intransigence of a dictator.

I asked him why the civilian population should be punished for Saddam Hussein's crimes. "It's a difficult problem," he replied. "You should realise that sanctions are one of the curative measures that the Security Council has at its disposal ... and obviously they hurt. They are like a military measure." "Who do they hurt?" "Well, this, of course, is the problem ... but with military action, too, you have the eternal problem of collateral damage." "So an entire nation is collateral damage. Is that correct?" "No, I am saying that sanctions have [similar] effects. We have to study this further."

"Do you believe that people have human rights no matter where they live and under what system?" I asked. "Yes." "Doesn't that mean that the sanctions you are imposing are violating the human rights of millions of people?" "It's also documented the Iraqi regime has committed very serious human rights breaches ..."

"There is no doubt about that," I said. "But what's the difference in principle between human rights violations committed by the regime and those caused by your committee?" "It's a very complex issue, Mr Pilger."

"What do you say to those who describe sanctions that have caused so many deaths as 'weapons of mass destruction' as lethal as chemical weapons?" "I don't think that's a fair comparison." "Aren't the deaths of half a million children mass destruction?" "I don't think that's a very fair question. We are talking about a situation caused by a government that overran its neighbour, and has weapons of mass destruction."

"Then why aren't there sanctions on Israel [which] occupies much of Palestine and attacks Lebanon almost every day of the week? Why aren't there sanctions on Turkey, which has displaced three million Kurds and caused the deaths of 30,000 Kurds?" "Well, there are many countries that do things that we are not happy with. We can't be everywhere. I repeat, it's complex." "How much power does the United States exercise over your committee?" "We operate by consensus." "And what if the Americans object?" "We don"t operate."

There is little doubt that if Saddam Hussein saw political advantage in starving and otherwise denying his people, he would do so. It is hardly surprising that he has looked after himself, his inner circle and, above all, his military and security apparatus.

His palaces and spooks, like the cartoon portraits of himself, are everywhere. Unlike other tyrants, however, he not only survived, but before the Gulf War enjoyed a measure of popularity by buying off his people with the benefits from Iraq's oil revenue. Having exiled or murdered his opponents, more than any Arab leader he used the riches of oil to modernise the civilian infrastructure, building first-rate hospitals, schools and universities.

In this way he fostered a relatively large, healthy, well-fed, well-educated middle class. Before sanctions, Iraqis consumed more than 3,000 calories each per day; 92 per cent of people had safe water and 93 per cent enjoyed free health care. Adult literacy was one of the highest in the world, at around 95 per cent. According to the Economist's Intelligence Unit, "the Iraqi welfare state was, until recently, among the most comprehensive and generous in the Arab world."

It is said the only true beneficiary of sanctions is Saddam Hussein. He has used the embargo to centralise state power, and so reinforce his direct control over people's lives. With most Iraqis now dependent on the state food rationing system, organised political dissent is all but unthinkable. In any case, for most Iraqis, it is cancelled by the sense of grievance and anger they feel towards the external enemy, western governments.

In the relatively open and pro-Western society that existed in Iraq before 1991, there was always the prospect of an uprising, as the Kurdish and Shia rebellions that year showed. In today's state of siege, there is none. That is the unsung achievement of the Anglo-American blockade.

The economic blockade on Iraq must be lifted for no other reason than that it is immoral, its consequences inhuman. When that happens, says the former UN weapons inspector Scott Ritter, "the weapons inspectors must go back into Iraq and complete their mandate, which should be reconfigured. It was originally drawn up for quantitative disarmament, to account for every nut, screw, bolt, document that exists in Iraq. As long as Iraq didn't account for that, it was not in compliance and there was no progress.

"We should change that mandate to qualitative disarmament. Does Iraq have a chemical weapons programme today? No. Does Iraq have a long-range missile programme today? No. Nuclear? No. Biological? No. Is Iraq qualitatively disarmed? Yes. So we should get on with monitoring Iraq to ensure they do not reconstitute any of this capability."

Even before the machinations in the UN Security Council in October and November 2002, Iraq had already accepted back inspectors of the International Atomic Energy Agency. At the time of writing, a new resolution, forced through the Security Council by a Bush administration campaign of bribery and coercion, has seen a contingent of weapons inspectors at work in Iraq. Led by the Swedish diplomat Hans Blix, the inspectors have extraordinary powers, which, for example, require Iraq to "confess" to possessing equipment never banned by previous resolutions. In spite of a torrent of disnformation from Washington and Whitehall, they have found, as one inspector put it, "zilch".

An attack is next; we have no right to call it a "war". The "enemy" is a nation of whom almost half the population are children, a nation who offer us no threat and with whom we have no quarrel. The fate of countless innocent lives now depends on vestiges of self-respect among the so-called international (non-American) community, and on free journalists to tell the truth and not merely channel and echo the propaganda of great power.

It is seldom reported that UN Security Resolution 687 that enforces the embargo on Iraq also says that Iraq's disarmament should be a step "towards the goal of establishing in the Middle East a zone free from weapons of mass destruction ..." In other words, if Iraq gives up, or has given up, its doomsday weapons, so should Israel. After 11 September 2001, making relentless demands on Iraq, then attacking it, while turning a blind eye to Israel will endanger us all.

"The longer the sanctions go on," said Denis Halliday, "[the more] we are likely to see the emergence of a generation who will regard Saddam Hussein as too moderate and too willing to listen to the West."

On my last night in Iraq, I went to the Rabat Hall in the centre of Baghdad to watch the Iraqi National Orchestra rehearse. I had wanted to meet Mohammed Amin Ezzat, the conductor, whose personal tragedy epitomises the punishment of his people. Because the power supply is so intermittent, Iraqis have been forced to use cheap kerosene lamps for lighting, heating and cooking; and these frequently explode. This is what happened to Mohammed Amin Ezzat's wife, Jenan, who was engulfed in flames.

"I saw my wife burn completely before my eyes," he said. " I threw myself on her in order to extinguish the flames, but it was no use. She died. I sometimes wish I had died with her." He stood on his conductor's podium, his badly burnt left arm unmoving, the fingers fused together.

The orchestra was rehearsing Tchaikovsky's Nutcracker Suite, and there was a strange discord. Reeds were missing from clarinets and strings from violins. "We can't get them from abroad," he said. "Someone has decreed they are not allowed." The musical scores are ragged, like ancient parchment. The musicians cannot get paper.

Only two members of the original orchestra are left; the rest have set out on the long, dangerous road to Jordan and beyond. "You cannot blame them," he said. "The suffering in our country is too great. But why has it not been stopped?"

It was a question I put to Denis Halliday one evening in New York. We were standing, just the two of us, in the great modernist theatre that is the General Assembly at the UN. "This is where the real world is represented," he said.

"One state, one vote. By contrast, the Security Council has five permanent members which have veto rights. There is no democracy there. Had the issue of sanctions on Iraq gone to the General Assembly, it would have been overturned by a very large majority.

"We have to change the United Nations, to reclaim what is ours. The genocide in Iraq is the test of our will. All of us have to break the silence: to make those responsible, in Washington and London, aware that history will slaughter them."

* This is an edited extract from John Pilger's latest book, "The New Rulers of the World"