Clare Short turned up the pressure on Tony Blair yesterday by accusing him of deceiving the Cabinet on three crucial elements of the Iraq crisis.
The failure to uncover any weapons of mass destruction - as well as claims that the Government doctored intelligence reports about them - has dogged every step of the Prime Minister's six-day tour of Europe and the Middle East.
News of the allegations overshadowed his morale-boosting address to British troops in Basra, Iraq, last week, and a press conference with Leszek Miller, the Polish Prime Minister, designed to highlight Britain's success in making new friends in eastern Europe.
Mr Blair has consistently played a straight bat to challenges over the absence of WMD. But allegations of dishonesty over the issue were repeated yesterday by Ms Short, who denounced as "spin" the claim that biological and chemical materials had been "weaponised" by Iraq.
The Prime Minister insists they will be uncovered but has also pleaded for patience as the search continues over the "coming weeks and months". He has also set considerable store by the discovery of two trailers, which Britain and America believe could have been used to make chemical and biological weapons.
Many Labour critics, including Ms Short, do not dispute that Saddam Hussein's regime experimented with chemical and biological agents. But they argue that the regime had not yet devised a way of arming missiles with such materials and that there was time for diplomatic initiatives to persuade Saddam to abandon his weapons programme. To win over the waverers, Allied forces must uncover clear evidence of WMD ready for use.
Mr Blair will probably succeed in his appeal to Labour sceptics to allow more time to find the elusive weapons. But he now faces questions on Ms Short's second charge, that he entered a pact with President George Bush in September last year to go to war in the spring.
Ms Short's accusation is unprovable, and deniable, but presents a serious problem for Mr Blair. Coming from a former member of hiswar cabinet, it is an incendiary allegation for Labour MPs who instinctively recoil against any suggestion of their leader stitching up secret deals with right-wing American Republicans.
If true - and it is fiercely denied by Downing Street - it would make a mockery of the Government's much-vaunted but futile efforts to win UN backing for military action.
Ms Short's also claimed that Mr Blair deliberately exaggerated the French government's opposition to military action to keep up the pressure for war.
Downing Street and the Foreign Office seized on comments by President Jacques Chirac in March that "France will vote 'no' because it considers this evening there are no grounds for waging war in order to achieve the goal we have set ourselves - to disarm Iraq".
Ms Short argued that a full reading of the transcript, which was sent to her by a member of the public, showed that M. Chirac was arguing for the process of weapons inspections to be completed, but that if it failed to disarm Iraq the UN would then have to approve military action.
Setting aside the question of whether Ms Short should have checked M. Chirac's precise words at the time, the accusation will carry weight. There is little doubt that the picture painted by ministers - of French intransigence - helped to stiffen the resolve for war.
After days of torrid publicity, Mr Blair's hopes when he touches down in London tomorrow - that Labour's agonies over Iraq might have eased - are likely to be dashed.
How the issue has dogged Tony Blair's globetrotting
28 May (Going to Kuwait City)
"I have said throughout ... I have absolutely no doubt about the existence of weapons of mass destruction. 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 we and the Americans believe were used for chemical and biological weapons."
29 May (Addressing troops in Basra, southern Iraq)
"I know there are a lot of disagreements in the country about the wisdom of my decision to order the action, but I can assure you of one thing, there is absolutely no dispute in Britain at all about your professionalism and your courage and dedication."
30 May (Warsaw)
"We have only just begun the process of investigating the various sites ... You have just got to have a little bit of patience. I have absolutely no doubt at all when we produce the further evidence, that evidence will be found and I have absolutely no doubt it exists because Saddam's history of weapons of mass destruction is not some invention of the British security services. It has been well documented over 12 years of lies and deception from Saddam."
31 May (St Petersburg)
"We have ... to investigate literally hundreds, possibly even thousands, of different sites. That work is only just beginning. What I have said to people is, over the coming weeks and months, that we will assemble this evidence and then we will give it to people. And I have no doubt whatever that the evidence of Iraqi weapons of mass destruction will be there. Absolutely."
1 June (Evian, France)
"Every single statement we have made that we said was based on intelligence was based on intelligence, cleared by the Joint Intelligence Committee. Any suggestion that we somehow manufactured the intelligence is completely and utterly false."Reuse content