Labour's rebels study rule book

Labour MPs dusted down their party rule books this weekend as they started to think the once unthinkable - how to topple Tony Blair.

Labour MPs dusted down their party rule books this weekend as they started to think the once unthinkable - how to topple Tony Blair.

His left-wing critics tried to trigger a leadership election in the last parliament but failed to muster the signatures of 20 per cent of the Parliamentary Labour Party, as required under the rules. On the face it, that hurdle is easier to jump after Thursday's general election, when the number of Labour MPs fell from 409 to 356. So the number of signatures required has dropped from 82 to 72.

Left-wingers collected the names of 62 MPs prepared to call for a leadership election last year. They are now confident of finding the necessary 72.

But the rulebook does not make clear whether a Prime Minister can be challenged; some senior Labour sources say the "20 per cent rule" applies only when the party is in opposition.

If they are right, the rebels might be forced to use a rule allowing the annual conference to call a special conference on whether there should be a leadership election. That would require a majority on a card vote at the annual conference, where the votes are split 50-50 between the trade unions and party members.

If a leadership election were held, it would be decided by an electoral college in which MPs, party members and trade unions each have a third of the votes.

However, Labour insiders believe Mr Blair's fate is unlikely to be sealed by a formal challenge. A more likely vehicle would be the equivalent of the Tories' "men in grey suits". If Mr Blair lost the confidence of a majority of his MPs, they would tell him his time was up.

Such a message could be delivered by the Parliamentary Committee, which is made up of the "shop stewards" representing Labour MPs and Cabinet ministers, who meet Mr Blair every Wednesday.

Probably the most crucial group in determining Mr Blair's length of tenure will be the Cabinet. He has said that he retains the "power of patronage" even though he will not fight another general election. But if the people he appoints to his Cabinet turn against him, the game will be up.