Gordon Brown's campaign team for the Labour leadership yesterday released astonishing figures showing the chancellor already has the support of 217 MPs with only 35 refusing to nominate him. A further 93 are undecided.

The overwhelmingly positive response from MPs suggests Mr Brown is on the verge of obliterating any opposition.

His canvassing team also unusually released some of the names of isolated senior MPs who are still holding out against the chancellor, and revealed they were intent on stopping a challenge from the party's left wing, most likely from John McDonnell.

The determination of Mr Brown's team to prevent Mr McDonnell, or the former home secretary, Charles Clarke, reaching the 44 nominations required to stand contrasts with Mr Brown's assertion earlier this week that he would welcome a contest for the leadership.

The chancellor's campaign manager, Jack Straw, has already formally launched the campaign by writing to each of the Labour MPs a fortnight ago, telling them that he was leading the Brown campaign, but others have been conducting detailed canvassing work.

The Brown camp is working on the assumption that Tony Blair will announce that he will stand down on May 9, the day after power sharing starts in Northern Ireland, and that the new premier will take over on July 15.

The Guardian was told that Labour MPs were still being contacted yesterday to be asked whether they would nominate the chancellor for leader, in a move to stop the left wingers Mr McDonnell or Michael Meacher gathering enough votes to stand, as well as to block a desperate last minute bid by a Blairite.

At 6pm yesterday Mr Brown had pledges from 217 Labour MPs. According to the canvass returns of the campaign team, several ministers and ex-ministers are among the 35 who have declined to nominate him.

They include John Hutton, the works and pensions secretary; Hilary Armstrong, the Cabinet Office minister; Stephen Byers, the former transport secretary; Alan Milburn, the former health secretary; Adam Ingram, the defence minister; Joan Ryan, a junior home office minister; Pat McFadden, a junior Cabinet Office minister (reported to be thinking of changing his mind); Claire Ward, a government whip; Jim Murphy, the employment minister; and Janet Anderson, a former culture minister.

According to the Brown team, the Meacher campaign is virtually dead in the water, with only three MPs expected to vote for him.

Mr McDonnell is doing much better - the most optimistic suggestion shows he is just five short of the 45 MPs he needs to stand. But the Brown camp hopes to convince at least 10 of his supporters to switch allegiances.

Mr Brown's supporters are also expecting a last-minute attempt by the Blairites to canvass three names - the former cabinet minister Charles Clarke; the home secretary, John Reid; and the environment secretary, David Miliband - as potential challengers if Labour performs badly in the elections for the Scottish parliament, Welsh assembly, and local councils on May 3.

Significantly, Mr Miliband, unlike Mr Clarke and Mr Reid, is not on the list of MPs who refused to support Gordon Brown. He is rated as "undecided" by campaigners, despite his recent public statement that he will be backing the chancellor.

The initiative to sign up and canvass the 355 MPs appears to be a pre-emptive strike to ensure Mr Brown has a tidal wave of support when Mr Blair stands down.