Gordon Brown’s enemies are preparing to accelerate a campaign for his removal from No 10 after he was left weakened by David Miliband’s move to stake a claim as Labour’s next leader.

Blairite ex-ministers including Charles Clarke and Stephen Byers will hold talks this week to decide on the timing of a series of statements and policy initiatives that they have prepared.

The group, working with Cabinet ministers and senior party figures, is preparing to keep up the pressure on the Prime Minister by challenging him on policy issues throughout this month. They hope that this will boost Mr Miliband, who called for a “radical new phase” of the Labour Party last week.

The meeting follows the leaking of a memo revealing Tony Blair’s fury with his successor for criticising his record. The memo accuses Mr Brown of “fatal” blunders.

Three senior ministers – Alistair Darling, Harriet Harman and John Denman – came to Mr Brown’s defence after No 10 ordered Cabinet members to voice support for him over the weekend.

But this did little to shore up the position of Mr Brown, whose woes deepened with the publication of the memo that disclosed Mr Blair was furious that his successor had “dissed” Labour’s record. He scorned Mr Brown’s approach in claiming he would abandon the “spin” of the Blair years and replace it with a more “honest” style.

Mr Blair criticised a “lamentable confusion of tactics and strategy” and concluded that Mr Brown “junked the [Blair] policy agenda but had nothing to put in its place”.

He even suggested that David Cameron’s fortunes were flagging before he left office, but that Mr Brown had allowed the Conservative policy initiatives to gain “traction”.

The memo, written after last year’s disastrous Labour Party conference in September, is believed to have been circulated around Mr Blair’s inner circle. A toned down version of his concerns and advice was later sent to Mr Brown.

Friends of Mr Blair said it accurately reflected his thinking last autumn but that it may not have been personally penned by the ex-Prime Minister, who is mentioned throughout in the third person.

Mr Miliband, who used to work for Mr Blair, was recently revealed to be in regular touch with the former Prime Minister, and the memo’s timing will be seen as part of an orchestrated Blairite plot to oust Mr Brown.

Downing Street refused to comment on the document obtained by the Mail on Sunday. A spokesman for Mr Blair did not deny the document was genuine, but stressed that he was “100 per cent behind Gordon Brown”.

It came as Mr Byers, an arch-Blairite, broke cover to issue a scathing verdict on Mr Brown’s chances of winning the next election. He called the Government’s platform “a multitude of small policies and worthy initiatives that are more suited to a Sunday afternoon stroll”.

The former Cabinet minister also said that there were “questions” over Mr Brown’s leadership and endorsed Mr Miliband’s call for change in the Labour Party.

Mr Byers also made the first move in the plan to outline an alternative policy agenda to Mr Brown’s, suggesting that council tenants be allowed to use their discount entitlement from the right-to-buy scheme as a deposit for buying a home.

“We will be releasing things over the next month. There is a gap here,” said one source.

The Prime Minister is pinning his hopes of a political recovery on a major reshuffle and an economic package in the autumn offering help for hard-pressed families after energy bills rose 35 per cent last week. Mr Brown is taking an intense personal interest in the option of a windfall tax or green energy tax, despite caution from John Hutton, the Business Secretary, and Alistair Darling, the Chancellor.

However, the timing of any relaunch could prove awkward for Mr Brown, with No 10 stressing the reshuffle will not be in the first week of September, leaving little time for ministers to read into their new briefs before conference. The annual party gathering in Manchester begins this year on September 20, which senior Cabinet figures set as the deadline for Mr Brown to turn his fortunes around.

This comes amid signs of nervousness in Downing Street at the failure of Cabinet ministers to spring to the defence of the Prime Minister.

Last week the No 10 political unit contacted members of the Cabinet to order them to take part in a Sunday newspaper survey on whether Gordon Brown should stay. Six of the 22 Cabinet members failed to respond, although many of those were on holiday.

“We got an e-mail saying it was OK to response to this survey. It is extraordinary that Number 10 should feel the need to send out such a message, and the first time I have ever experienced an operation like that,” said a Cabinet source.

Unions and Labour leftwingers have made it clear they would be highly unlikely to support a Miliband leadership bid. Yesterday Jon Cruddas, the prominent centre-left backbencher, accused Mr Miliband of “a narcissistic dash for personal glory” and gave a warning that voters will not forgive Labour for fighting among themselves.

Mr Cruddas, who came third in last year’s deputy leadership election, did not mention the Foreign Secretary by name, but there was little doubt his comments were directed at Mr Miliband.

Mr Cruddas wrote: “The past few days haven’t exactly been the Labour Party’s best . . . We have not exactly covered ourselves in glory with some unedifying behaviour by senior members of the party.

“Voters will forgive us for many things, but engaging in an internal row that would make student faction-fighting look pretty cool is not one of them.”

Mr Clarke said that he was on holiday and would not be taking part in discussions or speak about Mr Brown until he returned.

Times Recommends

• How I lost the gift of joy for a while
• Why Ann Widdecombe has got it wrong
• Alas, it’s the end of the road for petrolheads