UK plans in Iraq should be reviewed to match the strategy rethink in the US, the shadow foreign secretary has said.
British troops will stay until the 'job is done' says Des Browne
The government should give MPs a "frank" assessment of the changing situation, said William Hague.
"Clearly things are not going as well as many of us hoped they would... we do need to learn from that," he said.
He spoke as Defence Secretary Des Browne said Iraqi forces in the south could be capable of taking control of security in a year's time.
Mr Browne was echoing comments from Foreign Office Minister Kim Howells on Saturday that local forces should be able to take over within a year.
"Others may describe when they think the Iraqi forces may be able to take over their responsibility... and I agree with them in terms of capacity," he told Sky News.
He said the estimates were a reflection of the "improvement" there had been in the Iraqi forces.
In the US, Mr Bush's handling of the Iraq crisis has become a major issue in the elections next month for Congress. Opinion polls suggest his Republican party could lose control of the Senate and House of Representatives.
On Sunday a senior US state department official said the US had shown "arrogance and stupidity" in Iraq.
A review of American options is being carried out by former US Secretary of State James Baker - to be published after the 7 November elections.
Recent leaks have suggested the president will be advised to drop the "stay the course" policy in favour of preparing for an eventual exit strategy.
Mr Hague told BBC One's AM programme that the review going on in Washington should be mirrored by a "careful reassessment" in London.
"That work should be happening in Whitehall as well and we should be able to fully debate it in the House of Commons and know that there is British influence in the decision, not just solely an American decision."
He said Parliament had not had the opportunity for a full debate on the changing situation in Iraq since returning from the summer recess.
"We are certainly not in favour of a precipitate withdrawal or panic in this situation, but we are in favour of learning from experience," he said.
"That means we do now need that well-informed debate."
Liberal Democrat leader Sir Menzies Campbell said: "It is not tactics that matter in Iraq, but strategy.
"And the sooner the prime minister and president realise this, the better. The present strategy has failed."
A spokesman for the Foreign Office said the strategy had been clearly laid out by the prime minister in the Commons on Wednesday, and in Baghdad in May.
On Wednesday, Mr Blair said it was right to discuss the strategy - but added that it would not change, and that to withdraw prematurely would be "disastrous".
On Sunday, Mr Browne said Britain was "quite far down" the road toward transferring responsibility for security in Iraq to national security forces.
But, asked directly when he thought British forces would be out of Iraq, he replied only: "When the job is done".
Britain has about 7,000 troops stationed in southern Iraq around the second city of Basra.
Last week the head of the Army, General Sir Richard Dannatt, was quoted in the Daily Mail as saying British troops "exacerbated" Iraq's security problems and should withdraw "some time soon".