Comment Central: The reshuffle, as it happens...

James Purnell’s unexpected resignation last night electrified the initially chaotic “peasants’ revolt” by backbench MPs to unseat Gordon Brown.

Within an hour of his resignation letter appearing on Times Online, three backbench Labour MPs had called for Mr Brown to quit, and a fourth, a senior select committee chairman, demanded that the matter be put to a secret ballot. Mr Brown's fate will be determined within days with every Labour MP being put on the spot over whether he should stay or go.

Opponents have spent weeks figuring out how they could gauge the strength of opposition in a way that remained undetected by the Whips’ office and, when the time came, simultaneously declare their unhappiness. An e-mail was expected to be circulated, allowing them to sign up to oust the beleaguered Prime Minister.

But as polls closed on the European and local elections last night, the planning was overtaken by open warfare on the airwaves, with a string of backbenchers following Mr Purnell in calling for him to go.

Graham Allen, MP for Nottingham North, told Sky News that he hoped Mr Brown would “take the honourable way out so that the party can progress with a leadership election”. He added: “The Labour Party now needs fresh leadership. I hope that happens with Gordon Brown’s blessing. Gordon has given incredible service to the Labour Party.”

Nick Raynsford, the former local government minister, and Siobhain McDonagh, who was involved in last September’s coup attempt, also joined calls for him to quit.

Barry Sheerman, the normally loyal chairman of the Commons Schools Committee, told the BBC that the party should be allowed a secret ballot on whether Mr Brown should stay: “I think he would be asked to step aside if people were allowed a free vote.”

Others launched a desperate last-ditch attempt to rally round the Prime Minister. Geraldine Smith accused rebels of trying to “save their own skins” instead of thinking of the interests of the country.

Last night there was little sign of another Cabinet minister joining Mr Purnell, with David Miliband, the Foreign Secretary, John Hutton, Defence Secretary, Phil Woolas, Immigration Minister, and Caroline Flint, the Europe Minister, pledging support. David Blunkett, the former home secretary, called on the rest of the Cabinet to make their loyalty “unequivocably clear”.

MPs must decide whether to sign up to a group e-mail saying Mr Brown should leave Number 10, which would provide them with the relative safety of numbers.

Plotters claimed that individual groups of MPs had been organised in “terror cells” whose leaders never met, attempting to drum up support to force Mr Brown out.

One MP who owned up to being a plot organiser said: “It hurts us to have to do this. Most of us supported Gordon when he came in. It’s a sad fact that it hasn’t worked out. Nobody is getting any enjoyment out of this.

“But in the end, we are the peasants’ revolt. Gordon will not go unless one or two Cabinet ministers step up to the plate. We are doing what we can. In the end someone else has to be brave.”

Some plotters suggested that Charles Clarke, long an enemy of Mr Brown, had gathered at least 30 names, while Fiona McTaggart, a Blairite, could vouch for more than 40.

But the early leaking of the lofty ambitions of the plan led to a backlash yesterday amid fears that some plotters had exaggerated possible levels of support. The Prime Minister’s allies were quick to point out that any challenge involving only 50 MPs would have little impact since there were already 35 serial rebels in the party and this would not represent a significant change of mood.

Now they must show that this support does indeed exist.

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