Cabinet ministers will give Gordon Brown "one last chance" to save his premiership but will try to oust him by November if he fails to improve Labour's prospects.
Senior ministers believe that it would be a mistake to move against the Prime Minister before Labour's annual conference next month, which they are warning would then descend into a "shambles". One senior Labour source said: "We can't go on as we are. We have either got to get behind him or get rid of him. We can't do both."
One minister said yesterday: "It's not the right time to take a leap into the unknown. He deserves one last chance to turn it round and we should support him in that. He might be able to do it. If he can't, then we will have to take some big decisions and think through the consequences."
Even some of his cabinet critics appear ready to accept that Mr Brown should be allowed a final opportunity to revive his fortunes by unveiling an economic plan next month to help people struggling to cope with rising fuel, food and housing costs in the downturn. But they intend to force him out if his fightback flops and he fails to rally Labour at its Manchester conference.
The plan to give Mr Brown a temporary reprieve will disappoint Labour backbenchers who hoped that he would be ousted before the conference. David Miliband, the Foreign Secretary and frontrunner to succeed him, put down a marker about his leadership ambitions in a newspaper article last month.
Some backbench critics have not given up hope of persuading cabinet ministers to "ambush" Mr Brown next month by threatening to resign if he does not stand down. They say that such moves would not be advertised in advance as it might give him a chance to pre-empt them, possibly by reshuffling the Cabinet. But they concede that the prospects of an immediate move against him have receded during the holiday season.
Ministers will reassure the critics that they will seek to remove the Prime Minister "in October or November" if he fails to take his last chance. Some are prepared to resign if he refuses to stand down after being told he has lost their confidence.
Even some Brown allies admit he has only "one more shot" at convincing his own party he should lead it into the next general election.
Although some ministers have deliberately kept their heads down during the holiday period, the Cabinet is expected to close ranks behind Mr Brown when it holds its first meeting of the new political season on 8 September, in theWest Midlands.
They will discourage backbenchers from criticising Mr Brown, warning that it would play into the Tories' hands and overshadow the party conference in Manchester.
Tony Lloyd, the chairman of the Parliamentary Labour Party, is said to be urging backbenchers not to organise a "round robin" letter saying that Mr Brown should quit – a device used two years ago during an attempted coup to force Tony Blair to name a date for his departure from No 10. Ministers believe the present circumstances are different and that the "least bloody option" is for senior cabinet figures to persuade him to "go quietly" for the sake of the party.
Allies of Mr Brown insist he has no intention of doing so. Although they recognise that he needs to mount a convincing fightback, they say his critics are in danger of undermining his attempt to close the Tories' 20-point lead in the opinion polls.
Another reason for delaying any strike against the Prime Minister is that Labour faces a difficultby-election in his political backyard in Fife following the death of Mr Brown's friend John MacDougall, the Labour MP for Glenrothes.
* The Business Secretary, John Hutton, appeared to rebuke calls from more than 70 MPs for a windfall tax on energy companies as he warned consumers that the era of cheap energy was over. In an interview with the Daily Telegraph, he said there was "genuine concern" about the difficulties for families facing soaring heating costs this winter, adding that the Government was looking at what extra support it could provide.
Brown's recovery plan?
Downing Street and Whitehall are working frantically on an "economic plan" for the centrepiece of Gordon Brown's attempted fightback next month. This could cover:
One idea is a £150 one-off fuel voucher to help seven million families struggling to pay soaring gas and electricity bills. Eighty Labour MPs have called for a windfall tax on the energy companies but ministers may opt for raising extra money from emissions permits under the EU carbon-trading scheme.
Options include trying to revive the market by reducing or delaying stamp duty paid by home buyers; a saving scheme aimed at helping first-time buyers raise a deposit; and turning empty properties into social housing.
The Bank of England could reform its special liquidity scheme to allow banks to swap unmarketable but relatively good-quality mortgage-backed securities for government securities. In effect, the state would lend the banking system money to grant mortgages.