Passage of the constitution paves the way for parliamentary elections on December 15.

The result was denounced as a fraud by opponents and Sunni leaders gave warning that the charter could fuel yet more violence.

But on the day Iraq ushered in its new constitution, the US military death toll in the country reached another milestone. The Pentagon said the 2,000th fallen trooper was Staff Sergeant George Alexander, 34, who died of injuries sustained when a roadside bomb exploded next to his Bradley vehicle in Samarra, north of Baghdad.

Even as final results revealed an overwhelming endorsement of the constitution, which was drawn up under the guidance of the Shia and Kurdish interim government, the insurgency reached the normally quiet Kurdish city of Sulaymaniyah. Twelve people were killed in two car bombings against Iraq’s former human rights minister and an army base.

The referendum results had been delayed by ten days after charges of vote-rigging in the key swing province of Ninevah prompted a wide-ranging audit of the ballot. Officials said that they had found no evidence to support the Sunni accusations.

The final results showed 79 per cent of those taking part across the country backed the constitution and 21 per cent opposed it, with a 63 per cent turnout. Although voters in three Sunni-dominated provinces rejected the charter, the "No" vote in Ninevah fell short of a two thirds majority. The charter would have failed if two thirds of voters had rejected it in three or more provinces.

A spokesman for the electoral commission, Farid Ayyar, said: "It is a civilised step that puts Iraq on the path to democracy, to rebuilding our new Iraq." Laith Kubba, spokesman for Iraqi Prime Minister Ibrahim Jaafari, said the results marked a victory for the political process.

But Sunni leaders were bitter at the outcome, which thwarted their attempts to vote the constitution down after they had rallied their community — about 20 per cent of the population — to vote. The large turnout was the first time the once-dominant minority had mobilised to participate in the post-war political process, having boycotted previous ballots.

Saleh Mutlaq, a prominent Sunni politician who had briefly taken part in the drafting of the constitution, called the approved charter an American document that had nothing to do with the Iraqi people. He said: "It is clearly a forgery. No respectful forger would produce such an obvious fake that could be seen through so easily, it is not professional work by the forgers."

His comments reflected wider fears that Sunnis were again disillusioned with the political process. Many fear that if Sunnis cannot be wooed into taking part in December’s elections for Iraq’s first permanent post-war government, the bloody insurgency could drag on indefinitely.

Hussein al-Falluji, another Sunni politician, cautioned that the passage of a constitution that Sunnis saw as being manipulated by Washington could only lead to more bloodshed.

Mr Mutlaq said that in Ninevah’s provincial capital, Mosul, 80 per cent of the population had rejected the charter, which Sunnis believe could lay the groundwork for the disintegration of Iraq by allowing a loose form of federalism.

"Violence is not the only solution, if politics offers solutions so that we can move in that direction. But there is very little hope that we can make any gains in the elections," Mr Mutlaq said. "I call on the free world. I call on the United Nations to intervene."

Carina Perelli, the United Nations official overseeing the polling, praised a "very good job" by election auditors and said that Iraq should be proud of the commission.

London and Washington appeared to brush aside the Sunni objections, describing the constitution as another step towards a stable, democratic Iraq. "The Iraqi people have shown again their determination to defy the terrorists and take part in the democratic process," said Jack Straw, the Foreign Secretary, hailing the result as "an important step in the development of a democratic, stable and inclusive Iraq".

"It’s a landmark day in the history of Iraq," said Scott McClellan, the White House spokesman. "We congratulate the Iraqi people."

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