Former premier Tony Blair will cooperate "fully" with a new British probe into the Iraq war, officials said yesterday, as the government conceded the inquiry will have the power to apportion blame.

The main opposition Conservatives put a motion to Parliament yesterday calling for a re-think of the inquiry's remit, which was defeated by 299 votes to 260 - but only after six hours of passionate debate.

Foreign Secretary David Miliband said the investigation, announced last week to fulfil a pledge for a probe once British troops have mostly left Iraq, would be independent and able to criticise whoever it wants.

"It can praise or blame whoever it likes. It is free to write its own report at every stage," Mr Miliband said, in what was widely seen as a concession on the remit of the probe originally intended only to learn lessons from the war.

He was speaking during a parliamentary debate sparked by an opposition call to rethink the inquiry's terms of reference. Concerns were raised about how much of the inquiry would be conducted behind doors and whether witnesses would be under oath.

In a sign of the controversy that awaits the inquiry, lawmakers said vital questions remained in particular about the reasons for going into war - the weapons of mass destruction Iraq was alleged to have had were never found - and how much Cabinet ministers were told.

There has been much speculation over whether Mr Blair, who controversially took Britain into the 2003 Iraq war alongside then US president George W. Bush, would give evidence - and crucially, whether it would be in public.

The former Prime Minister's spokesman said Mr Blair would cooperate with the probe, chaired by Sir John Chilcott, whatever its format.