The government has survived an attempt by the Conservatives to force an immediate independent inquiry into the decision to go to war in Iraq.
So far 175 British troops have been killed in Iraq
The call, which was supported by the Liberal Democrats and 12 Labour rebels, was defeated by 299 to 271 votes.
That more than halved the government's majority of 67.
A government amendment, recognising an inquiry will be "appropriate" but only after "important operations" in Iraq end, was passed by 299 to 259 votes.
Gordon Brown had said before Tuesday's votes that there would be an inquiry when it was appropriate, but to hold one now would be a diversion for UK troops serving in Iraq.
The Conservatives used the fifth anniversary of the US-led invasion of Iraq and their opposition-led debate to step up pressure on Mr Brown to hold an independent, public inquiry.
Opening the debate, shadow foreign secretary William Hague said now was the right time for a probe, before files and e-mails disappeared and memories faded.
He told MPs the government would have no choice but to hold an inquiry if they voted for one.
He said he did not regret voting for the US-led invasion in 2003, but it was "vital" to learn "all possible lessons" from the decisions that led to war and the failures in post-war planning.
He rejected claims that an inquiry would divert attention from the rebuilding of Iraq as "ludicrous".
And he also rejected the government's argument that it would damage the position of UK troops in Iraq.
Mr Hague told MPs: "The truth is that the case for commencing an inquiry of the type or of a similar type to the one we are calling for today has become overwhelming.
"If ministers continue to argue against it they will be isolated voices, holding out against a preponderance of national opinion which embraces every other party and many members of their own."
'Mission not accomplished'
Foreign Secretary David Miliband insisted that an inquiry would be necessary, but not until British troops had finished their work in Iraq.
He said: "The dispute between us does not concern substance but timing."
He said "most people" would see an inquiry as a "bizarre choice of priority now" given current events in Basra, where the remaining British troops in Iraq are stationed.
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.
"The mission has not yet been accomplished."
The Tory motion called for a full inquiry by an independent committee of privy councillors to be established now.
The government's majority was almost halved to 35 last June when MPs rejected a similar Conservative motion by 288 votes to 253.
Prior to Tuesday's vote, Edward Davey , Liberal Democrat foreign affairs spokesman, said the Tories would stand a better chance of winning if they admitted regret for voting for the war in the first place.
Mr Davey said "we owe an inquiry to the people who have died" in Iraq and delaying it was "nothing short of a scandal".
The 12 Labour MPs who supported Conservative calls for a full-scale inquiry were:
Harry Cohen (Leyton & Wanstead)
Jeremy Corbyn (Islington North)
Mark Fisher (Stoke-on-Trent Central)
Paul Flynn (Newport West)
Kelvin Hopkins (Luton North)
Lynne Jones (Birmingham Selly Oak)
John McDonnell (Hayes and Harlington)
Bob Marshall-Andrews (Medway)
Gordon Prentice (Pendle)
Linda Riordan (Halifax)
Alan Simpson (Nottingham South)
Sir Peter Soulsby (Leicester South)