The British and American governments are under pressure to explain how they reached the conclusion that the threat posed by Iraq's arsenal of illegal weapons justified going to war.
Calls have been made for a special committee of privy councillors - preferably security-cleared members of the House of Lords - to investigate Mr Blair's claims on weapons of mass destruction and the quality of intelligence presented to Parliament and the public before the war.
In the US, the Central Intelligence Agency is carrying out a review of how information on Iraq was gathered, but some senators are calling for an independent and public investigation.
The head of the CIA, George Tenet - also under pressure from a group of retired intelligence analysts who have publicly complained to President George Bush about misuse of secret information "to mislead our elected representatives" into voting for a war - has made a highly unusual public defence of the agency.
Writing for The Independent on Sunday, former Foreign Office minister Tony Lloyd, who rebelled against the Government in the crucial votes on Iraq leading up to the war, said: "In the end only an inquiry into the competence and probity of the security services and the way in which the intelligence they provided was used is going to put back the nation's trust. "Brutally, without that, it is the authors of the war within the Government whose credibility is once more on the line." Mr Lloyd added that MPs were "entitled to be angry if they have been but bit players in Donald Rumsfeld's war games".
Former defence minister Peter Kilfoyle, whose Commons motion demanding the publication of the evidence and its sources used to support a pre-emptive war, has attracted 75 signatures - many of them Labour - said: "What is well established now is that there are grave doubts amongst the intelligence community, amongst the weapons inspectors and leading lights in the US administration that Iraq had these much-vaunted weapons.
"The idea they had this vast arsenal about to be launched at 45 minutes is just risible nonsense."
On Wednesday, the parliamentary Intelligence and Security Committee meets behind closed doors to examine the Government's pre-war claims on Iraq.
It is uncertain, however, whether the committee will be allowed to see the detail of the intelligence reports that led to the Government's controversial September 2002 dossier that asserted Saddam Hussein's biological and chemical weapons could be deployed at 45 minutes' notice.Reuse content