In the first such event since the furore over John Prescott's croquet "awayday" at Dorneywood, Mr Blair is certain to be asked why he has hung onto the Deputy Prime Minister in the face of calls from some Labour MPs for him to go.

And he is likely to be quizzed over how long he can remain in place as Prime Minister if the man who has been his deputy since he became Labour leader in 1994 stands down.

The conference comes in the wake of a series of opinion polls putting David Cameron's Conservatives as much as 10 points ahead of Labour for the first time since the 1980s, raising new speculation over whether Mr Blair remains an electoral asset for the party.

Mr Prescott agreed to give up his grace-and-favour country residence in Buckinghamshire after the publication of photos of him playing croquet on the lawn on a week-day afternoon.

But questions remain over his future.

Labour MPs have openly discussed the succession, while Education Secretary Alan Johnson has said in public that he would like to be considered as the next DPM.

Others reported to be lobbying behind the scenes include Leader of the Commons Jack Straw, Northern Ireland Secretary Peter Hain and constitutional affairs minister Harriet Harman - who was thought by some observers to be making a none-too-subtle bid for the post when she said the next DPM should be a woman.

Speculation over Prescott's future has reignited discussion about the timing of Mr Blair's own departure.

Some commentators believe that a contest for the deputy's job would inevitably trigger a leadership election, as Mr Blair has already made clear he will be stepping down within the next year or two and the party may not want two polls in such quick succession.