Nouri al-Maliki, the Iraqi Prime Minister, is battling to survive a political crisis after losing almost half his Cabinet to boycotts and resignations after a spate of disputes over policy and performance.

In the latest blow, four secularist ministers who are loyal to Ayad Allawi, a former interim Iraqi leader, withdrew from Cabinet meetings, less than a week after the main Sunni bloc quit. Both groups blamed a failure by Mr al-Maliki to respond to demands for political reform.

The move took away the last remaining ministers with any Sunni political affiliations, effectively robbing the Shia-led Government of the national unity status that is seen as crucial by the US. The crisis comes at a pivotal moment for President Bush as Congress awaits a report on both security and the political situation in Iraq after a hotly contested surge of US troops in and around Baghdad.

“It is a big challenge to the [Iraqi] Government,” a Western diplomat said. “I think in some ways it is a moment of truth for how they might handle this particular problem.”

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Seventeen ministers have walked out of the Government, tendered their resignation or withdrawn from Cabinet meetings in recent weeks, frustrating efforts by Mr al-Maliki to make demonstrable progress in reconciling Iraq’s sectarian divisions in time for the US report in mid-September.

Hopes rest on the leadership of the rival parties agreeing a new power-sharing deal.

Mr al-Maliki, who visited Turkey yesterday, failed to strike a conciliatory tone in an interview with Iran’s Arabic language television channel Al-Alam. “The withdrawal from the Government is evidence of irresponsibility,” he said. “All this makes us believe that it is a sign of their lack of credibility and lack of sincerity in the political process, or a sign of a different agenda which is contrary to the political agenda we currently have.”

Mr Bush’s National Security spokesman, Gordon Johndroe, said that the Sunni defections were part of the “jockeying and posturing” among Baghdad’s political groups, and was not unexpected. He said that the Bush Administration remained committed to the al-Maliki Government. “They are working through a challenging set of circumstances and it is going to take some time,” he told The Times.

Kamaal al-Deen al-Qasem, a Professor of Politics at Baghdad University, said that Mr Allawi’s political group and the Sunni Accordance Front, which withdrew its support last week, appeared to be taking advantage of the Government’s weakened state to score political points. “They want the Government to collapse and this is the standard means of doing so,” he said.

Mr al-Maliki took the helm of Iraq’s democratically elected administration last year, raising hopes for reconciliation between the country’s mix of majority Shia Arabs, minority Sunni Arabs and Kurds. So far his Government’s performance has fallen far short of expectations. Sectarian rivalries between political parties remain strong, security is poor, and basic services such as water and power remain patchy at best.

The Electricity Ministry has warned that Iraq’s national power grid is on the brink of collapse. Water supplies to Baghdad have also been cut off for long periods.

Having trounced the Liberal Democratic Party in parliamentary elections in Japan, Ichiro Ozawa threatens to derail an anti-terrorism law on which substantial US military operations depend (Leo Lewis writes). The president of the Democratic Party of Japan, which now has an Upper House majority, opposes the extension of the law — passed after the 9/11 attacks to help the US to refuel aircraft and vessels in the Indian Ocean — when it runs out on November 1.

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