After weeks of tense negotiations, the debate about how to accommodate the country’s main Sunni, Shia and Kurdish communities seemed as fraught as ever last night and there were fears that the dispute could provoke even more bloodshed.

“We hope that this constitution will be accepted by all Iraqis and that it will be for everybody,” said President Talabani, the Kurdish head of state. “We are optimistic . . . For sure there is no book that is perfect and cannot be amended except the holy Koran.”

But even at his own ceremony there were hints of dissent within the ranks of the Iraqi leadership. Ghazi al-Yawer, Vice-President and a Sunni, failed to attend the event. An embarrassed Mr Talabani explained unconvincingly that his deputy was “sick”.

A more plausible explanation was that he was under pressure from his community not to be seen endorsing a document that many Sunnis believe discriminates against them.

Fellow Sunni leaders, representing the once-dominant community in Iraq, vowed not only to campaign for a “no” vote at the referendum on October 15 but also to notify international organisations that the charter was unrepresentative of the Iraqi people.

“We declare that we don’t agree and we reject the articles that were mentioned in the draft and we did not reach consensus on them in what makes the draft illegitimate,” said Abdul-Nasser al-Janabi, a member of the Sunni delegation on the constitutional committee. “We call upon the Arab League, the United Nations and international organisations to intervene so that this document is not passed and so that the clear defect in it is corrected.”

The Sunnis are particularly unhappy that the constitution described Iraq’s political system as “republican, parliamentary, democratic and federal”.

They believe “federal” will open the way for the creation of a Kurdish-mini state in the north and a Shia region in the south, which would not only control political affairs and security but also have access to the country’s huge oil wealth located in those regions.

The constitution also called for the banning of “Saddam’s Baath” Party, which some fear could lead to a purge of many Sunni professionals, who had joined the ruling party under the old regime.

If the Sunni “no” campaign is to succeed, its leaders need to mobilise a two thirds majority in three of Iraq’s 18 provinces. Sunnis have a majority in two, but the areas are also the most violent, making elections and campaigning very difficult.

In spite of the dispute, President Bush and Tony Blair last night praised the constitution as a landmark in Iraq’s political development. In the face of escalating violence, both Washington and London are desperate for any achievement that may usher in a stable government in Baghdad and ultimately hasten the withdrawal of foreign troops.

Speaking from his ranch in Crawford, Texas, Mr Bush reminded Americans that the US Constitution was vigorously debated in 1787 and its passage was not guaranteed. He congratulated the Iraqis on completing the next step in the transformation from “dictatorship to democracy”.

Mr Blair broke from his holiday in Barbados yesterday to issue a statement setting out the Government’s determination to continue working for a democratic and united Iraq.

He praised the Iraqis for succeeding “in drafting this constitution despite the action of terrorists who are trying to destroy the country’s desire for a peaceful future”.

He added: “The small minority who have chosen violence over democracy will no doubt respond with bloodshed and intimidation. But they can be defeated if Iraq’s communities work together to build a unified Iraq in which the rights and interests of all are respected.”

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