The report, which was not denied by a spokesman for Mr Blair yesterday, said the MPs were ready to join Labour if Kenneth Clarke, the Chancellor of the Exchequer, had resigned over the Prime Minister's plan to promise a referendum on a single European currency.
A further defection would wipe out John Major's Commons majority - cut to one by the election of Labour's Brian Jenkins in Staffordshire South East last week. The Government's survival in a vote of confidence would then depend on the nine-strong Ulster Unionist Party, led by David Trimble, and Ian Paisley's three Democratic Unionist Party MPs.
Speculation yesterday centred on strong pro-Europeans, including Peter Temple-Morris, Edwina Currie, Julian Critchley, Quentin Davies, Sir David Knox and Hugh Dykes.
Mr Temple-Morris, who recently set up a "One Nation" Tory think-tank called the Macleod Group, was in trouble with some members of his local Tory association in Leominster. But the rebels were unable to muster the 50 signatures required on a petition to reopen the choice of the urbane, white-haired former solicitor as the Tory candidate for the next election. Mr Temple-Morris was for years the leader of the "One Nation" Tory faction in the Commons, as head of a group called the Lollards which organised to win internal elections to backbench committees. His factional instincts - "we have to stay and fight" - suggest he will be loyal, but his grave manner conceals a wicked enjoyment of ideological battle which might tempt him to go.
Mrs Currie has been intensely frustrated by the failure of pro-Europeans in all parties, but especially the Tories, to push their arguments more vigorously. In recent months she has worked closely with Labour MPs Giles Radice and Peter Mandelson in the cross-party European Movement to promote the arguments for a single currency.
She built her reputation as a combative and partisan Tory, but has espoused causes - such as equal rights for homosexuals - more in tune with the Liberal Democrats or possibly Labour than her own party.
Mr Critchley, biographer of the Deputy Prime Minister, Michael Heseltine, publicly warned that he would vote against a referendum on a single European currency - not that the promise, which will go in the Tory manifesto, will be voted on in the Commons until after the election, if ever. He is unwell, but still comes to the Commons for knife-edge votes.
All of these suspects have been forced recently into denials that they are considering crossing the floor of the House.
Tory pro-Europeans would have been heartened, however, by the weekend declaration by their standard bearer, the Chancellor, that Britain would still be able to join a single currency if it were launched in 1999 - even if it did not join a new exchange rate mechanism.
But the depths of Tory pessimism about the general election, which must be held within 13 months but increasingly looks like being earlier, was underlined by a Sunday Times survey of MPs.
Of 100 Tories questioned, 46 said they thought Labour would win, and a further 20 predicted a hung Parliament.
Peter Temple-Morris, 58, said in an interview last month that if he had his time in politics again he would probably join "New Labour".
Edwina Currie, 49, stood - unsuccessfully - for the European Parliament two years ago, regarding it as more important than Westminster.
Julian Critchley, 65, is totally against a referendum and, even before last week's by-election warned, of Mr Major's one-vote majority: "I'm it."
Quentin Davies, 51, nearly ensured the Government was defeated over the Scott report on arms-to-Iraq, and has since advocated a single currency.
Sir David Knox, 62, co-signed a letter headlined "Single currency not a pipe dream" to the Times in December, but has promised to stay loyal.
Hugh Dykes, 56, declared he was "a lifelong Tory", but rebelled in last year's EU fish quotas vote - in protest at Mr Major's Euro-sceptical stance.