Prime Minister Gordon Brown was yesterday urged to give way to mounting calls for an immediate Privy Council inquiry into the origins and conduct of the Iraq war.

Shadow Foreign Secretary William Hague said in the Commons there was already a cross-party consensus that such an inquiry would be needed at some point.

But while the government had agreed in principle, it continued to insist it was not appropriate while British troops are still in Iraq.

"The case I wish to put to this House now is that the nation expects, our troops deserve and the facts lead to a fresh conclusion that the time to commence such an inquiry has indeed now been reached," Mr Hague told MPs.

"The passage of time, the urgent need to learn for the future, the need to reinforce the credibility of future decision-taking and the diminished role in Iraq of British forces all point to that clear conclusion."

Foreign Secretary David Miliband insisted an inquiry would be required but not until British troops had finished their work in Iraq. He said: "There is agreement that an inquiry into the Iraq war will be necessary.

"The dispute between us does not concern substance but timing.

"We say - in the words of the Prime Minister on March 19 - the right time to look at these issues and review the lessons learned is when our troops have finished their work in Iraq'."

He added: "The war itself went better than most people expected, but the building of the peace afterwards has gone much worse than people expected."