In a solemn ceremony which avoided all talk of victory, Dr Rowan Williams pointedly referred to Iraq as a “ravaged and deeply traumatised nation” after the invasion by British and US forces.

The Archbishop, who opposed the war and ensured that references to “thanksgiving” were removed, left the watching Prime Minister to ponder whether it would be the voters or God who would ultimately call him and the US President to account.

But in an apparent reference to the failure to find weapons of mass destruction six months after the end of the conflict, he also warned Mr Blair: “We have to go back and test what has happened in the light of the original vision.”

The Prime Minister, who listened with the Queen and Iain Duncan Smith, the Tory leader, has previously said that he was “ready to meet my Maker” and answer for those who died in the war.

In a carefully crafted political address, Dr Williams said that the service of remembrance at St Paul’s was an opportunity for political leaders to renew their promises about “remaking a deeply traumatised nation”.

Addressing a 2,000-strong congregation that also included Geoff Hoon, the Defence Secretary, and 14 members of the Royal Family, the Archbishop said: “We have made ourselves accountable for peace and justice in Iraq, and leaders and people alike will indeed be called to account.”

Michael Ancram, the Shadow Foreign Secretary, who attended the service, said later that Mr Blair was avoiding full accountability by rejecting calls for a judicial inquiry.

He told The Times: “We are all accountable for judgments we make politically. The Prime Minister, in our view, should allow a full judicial inquiry to enable the public to be aware of all the background in the lead-up and aftermath of the war.”

Downing Street said last night that Mr Blair stood by his assertion that he would make the same decision again over going to war.

But Mike Aston, whose son Russell was one of six Royal Military Police killed by an Iraqi mob in June, criticised the Prime Minister after the service. “My opinion has never been high, but now couldn’t get more than rock bottom, the way he’s conducted himself since the war started.”

Dr Williams, a critic of the war before hostilities began, was silent during the fighting out of respect for the Armed Forces and others involved.

Yesterday’s sermon marked his re-entry into the political arena over Iraq.

Questioning whether the original vision set out as the justification for going to war still stood up, he said: “As we look out at a still uncertain and dangerous landscape, as we recall the soldiers and civilians killed since the direct military campaign ended, as we think of the UN personnel and the relief workers who have died, we have to acknowledge that moral vision is harder to convert into reality than we should like.

“We never know in advance quite what price will have to be paid in human lives, civilian and military, local and foreign, young and old.”

Dr Williams’s warning that political leaders will be called to account had religious as well as political overtones.

It was an echo of the Prime Minister’s own belief, disclosed in Sir Peter Stothard’s behind-the-scenes account of the Iraq crisis, that he will be called to account for the Iraq war before God. “I’m ready to meet my Maker and answer for those who have died as a result of my decisions,” Mr Blair told Sir Peter, former Editor of The Times.

Dr Williams also acknowledged powerful arguments in favour of war: “Those who defended the action in Iraq rightly reminded us that while we talk, people are suffering appallingly; while we try to keep our hands clean, atrocity and oppression reign unchecked.”

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