Tony Blair stood accused last night of misleading Parliament and the British people over Saddam Hussein's weapons of mass destruction, and his claims that the threat posed by Iraq justified war.
Robin Cook, the former foreign secretary, seized on a "breathtaking" statement by the US Defence Secretary, Donald Rumsfeld, that Iraq's weapons may have been destroyed before the war, and anger boiled over among MPs who said the admission undermined the legal and political justification for war.
Mr Blair insisted yesterday he had "absolutely no doubt at all about the existence of weapons of mass destruction".
But Mr Cook said the Prime Minister's claims that Saddam could deploy chemical or biological weapons within 45 minutes were patently false. He added that Mr Rumsfeld's statement "blows an enormous gaping hole in the case for war made on both sides of the Atlantic" and called for MPs to hold an investigation.
Meanwhile, Labour rebels threatened to report Mr Blair to the Speaker of the Commons for the cardinal sin of misleading Parliament - and force him to answer emergency questions in the House.
Mr Rumsfeld ignited the row in a speech in New York, declaring: "It is ... possible that they [Iraq] decided that they would destroy them prior to a conflict and I don't know the answer."
Speaking in the Commons before the crucial vote on war, Mr Blair told MPs that it was "palpably absurd" to claim that Saddam had destroyed weapons including 10,000 litres of anthrax, up to 6,500 chemical munitions; at least 80 tons of mustard gas, sarin, botulinum toxin and "a host of other biological poisons".
But Mr Cook said yesterday: "We were told Saddam had weapons ready for use within 45 minutes. It's now 45 days since the war has finished and we have still not found anything.
"It is plain he did not have that capacity to threaten us, possibly did not have the capacity to threaten even his neighbours, and that is profoundly important. We were, after all, told that those who opposed the resolution that would provide the basis for military action were in the wrong.
"Perhaps we should now admit they were in the right."
Speaking as he flew into Kuwait before a morale- boosting visit to British troops in Iraq today, Mr Blair said: "Rather than speculating, let's just wait until we get the full report back from our people who are interviewing the Iraqi scientists.
"We have already found two trailers that both our and the American security services believe were used for the manufacture of chemical and biological weapons."
He added: "Our priorities in Iraq are less to do with finding weapons of mass destruction, though that is obviously what a team is charged with doing, and they will do it, and more to do with humanitarian and political reconstruction."
Peter Kilfoyle, the anti-war rebel and former Labour defence minister, said he was prepared to report Mr Blair to the Speaker of the Commons for misleading Parliament. Mr Kilfoyle, whose Commons motion calling on Mr Blair to publish the evidence backing up his claims about Saddam's arsenal has been signed by 72 MPs, warned: "This will not go away. The Government ought to publish whatever evidence they have for the claims they made."
Paul Keetch, the Liberal Democrat defence spokesman, said: "No weapons means no threat. Without WMD, the case for war falls apart. It would seem either the intelligence was wrong and we should not rely on it, or, the politicians overplayed the threat. Even British troops who I met in Iraq recently were sceptical about the threat posed by WMD. Their lives were put at risk in order to eliminate this threat - we owe it to our troops to find out if that threat was real."
But Bernard Jenkin, the shadow Defence Secretary, said: "I think it is too early to rush to any conclusions at this stage; we must wait and see what the outcome actually is of these investigations."
Ministers have pointed to finds of chemical protection suits and suspected mobile biological weapons laboratories as evidence of Iraq's chemical and biological capability. But they have also played down the importance of finding weapons of mass destruction in Iraq. Earlier this month, Jack Straw, the Foreign Secretary, provoked a storm of protest after claiming weapons finds were "not crucially important".
The Government has quietly watered down its claims, now arguing only that the Iraqi leader had weapons at some time before the war broke out.
Tony Benn, the former Labour minister, told LBC Radio: "I believe the Prime Minister lied to us and lied to us and lied to us. The whole war was built upon falsehood and I think the long-term damage will be to democracy in Britain. If you can't believe what you are told by ministers, the whole democratic process is put at risk. You can't be allowed to get away with telling lies for political purposes."
Alan Simpson, Labour MP for Nottingham South, said MPs "supported war based on a lie". He said: "If it's right Iraq destroyed the weapons prior to the war, then it means Iraq complied with the United Nations resolution 1441."
The former Labour minister Glenda Jackson added: "If the creators of this war are now saying weapons of mass destruction were destroyed before the war began, then all the government ministers who stood on the floor in the House of Commons adamantly speaking of the immediate threat are standing on shaky ground."
The build-up to war: What they said
Intelligence leaves no doubt that Iraq continues to possess and conceal lethal weaponsGeorge Bush, US President 18 March, 2003
We are asked to accept Saddam decided to destroy those weapons. I say that such a claim is palpably absurdTony Blair, Prime Minister 18 March, 2003
Saddam's removal is necessary to eradicate the threat from his weapons of mass destructionJack Straw, Foreign Secretary 2 April, 2003
Before people crow about the absence of weapons of mass destruction, I suggest they wait a bitTony Blair 28 April, 2003
It is possible Iraqi leaders decided they would destroy them prior to the conflictDonald Rumsfeld, US Defence Secretary 28 May, 2003