Robin Cook delivers a fresh and devastating blow to Tony Blair today by claiming that serving British ambassadors support the 52 former diplomats who criticised the Prime Minister over his policy on the Middle East.
The former foreign secretary's remarks will infuriate Mr Blair, whose leadership was the subject of open speculation among Labour MPs last night following the backlash among his cabinet allies over his U-turn on the EU referendum.
Mr Cook, writing in The Independent, says it is inconceivable that agreement on a common text could have been reached among the former diplomats "without widespread sympathy for their views among the ambassadors who have replaced them".
Underlining the unprecedented importance of their letter, Mr Cook adds: "By the standards of diplomatic communiqués, their statement is off the Richter scale."
Mr Blair will defend his position today at Prime Minister's Questions, but Labour backbench MPs were saying privately that the diplomats had delivered a devastating blow to Mr Blair's authority, already damaged by his U-turn on the EU constitution. Mr Blair suffered more criticism yesterday after announcing a review of immigration policy, which was seen as an admission that previous initiatives had failed.
Mr Blair criticised the former diplomats for being unbalanced in their criticism of his support for President George Bush and the deal with Ariel Sharon, the Israeli Prime Minister, which critics say will tear up the Middle East road map.
Following talks in Downing Street with his Italian counterpart Silvio Berlusconi, Mr Blair acknowledged the "frustration" of the former diplomats over the Middle East. However, he said the coalition had to ensure Iraq did not fall into the hands of "fanatics and terrorists" - language dismissed as "neither convincing nor helpful" by the former diplomats in their letter.
The former envoys said that if Britain was unable to exert "real influence" on the US administration, it should abandon its support policies which were "doomed to failure".
Jack Straw, the Foreign Secretary, warned against attempts to drive a wedge between London and Washington. He told BBC Radio 2's Jeremy Vine show: "It is very important for us to try to work with the United States and not to have a polarisation that would weaken our influence and weaken the influence of Europe."
Labour MPs said the Foreign Office shared the view of some of the former diplomats. One former minister close to Mr Blair said the diplomats had complained that Downing Street had seized control of foreign policy from the Foreign Office.
Left-wing Labour MPs who backed the former diplomats predicted last night that Mr Blair would step down before the general election. Jeremy Corbyn, a member of the Campaign Group, said: "I think Blair is ready to go. He looks increasingly out of sorts. It is past the time when Blair should recognise foreign policy should not be decided in the West Wing." Three of Mr Blair's former allies, including Peter Mandelson, who wrote a joint article in The Guardian yesterday, are privately pressing for Mr Blair to reassert his leadership on Europe in the European elections.
One former Labour minister said: "I think Tony recognises that a lot needs to be done. We need to get a grip organisationally, within the Labour Party and outside, to sort out how we are going to match the anti-European campaign. We need to re-establish a body like Britain in Europe to run the "yes" campaign for the constitution, and we need to do that now."
Labour MPs will express their support for the former ambassadors' letter tomorrow. A clutch of Labour MPs will back the former ambassadors' call for a change of direction and urge Tony Blair to make it clear he does not back Mr Sharon's plan for the Middle East.
Richard Burden, the chair of the All Party Britain-Palestine Parliamentary Group, said Mr Blair would be advised to listen to the former ambassadors who are "very serious people" who have "a great deal of experience in the Middle East". A total of 108 MPs have signed Mr Burden's parliamentary motion voicing "strong concerns" over Mr Bush's endorsement of Mr Sharon's plans.
Joan Ruddock, the Labour MP for Lewisham Deptford, said the former ambassadors were reflecting concerns of a huge number of Labour backbenchers. "I hope that the Prime Minister recognises that these sentiments are very widely held in the Parliamentary Labour Party," she said.