A new group of Labour politicians warned today that the party appeared “intellectually exhausted” and could be out of power for a generation unless it produces fresh ideas soon.

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The group, including nine former ministers, fired a warning shot at Gordon Brown by urging him to ensure that Labour fights the next general election on a forward-looking manifesto. They denied that their joint pamphlet and “Labour Future” website was part of a plot to oust the Prime Minister before the general election.

The group’s opening statement said Labour faced a "strong" chance of being swept out of office for a generation, as it was during 18 years of Tory rule from 1979. Despite Mr Brown's efforts to set out his vision, there remained a "widespread perception that Labour... is intellectually exhausted.

"It is a strong perception and it needs to be countered with a positive agenda and intellectual confidence," it said, suggesting Labour lacked "a clear progressive agenda".

Malcolm Wicks, the Prime Minister’s envoy on international energy matters, who is leading the initiative, told a press conference: “We are not some partisan faction within the Labour Party. We have to be honest about it: we are in something of a malaise.”

He admitted that a betting man would not bet on Labour winning the next election. "We have got to come up with fresh thinking and fresh policies if we are to be credible as I believe we can be in terms of the next election,” he said.

Charles Clarke, the former Home Secretary, who has called for Mr Brown to stand down, insisted the new group was about stimulating ideas - not destabilising the Prime Minister.

"It is unfortunate and also inaccurate to interpret it as an act which is inspired by a desire to change the leadership. It is not," he said. "My views are well known on this subject and I am not resiling from them or repeating them. I don't think Gordon Brown would regard this as an enemy act. I think he wants to engage in this kind of debate and we need more of it.”

Ideas put forward by the 10 individual members of the group include reducing the role of the Navy and RAF to fund Army operations, a minimum alcohol price, scrapping child-related tax credits to provide universal services for young people, earmarked taxation and more charges for public services.

Although the group will avoid direct criticism of Mr Brown, Labour MPs are privately discussing his future again. He received a rough ride on Monday when he addressed their weekly private meeting and urged them to make any repayments demanded by Sir Thomas Legg, the former Whitehall mandarin auditing the claims of all MPs.

Some Labour insiders say the anger of the party’s MPs about the Legg review, ordered by Mr Brown in May, has increased the chances of a new push to topple the Prime Minister.

But others say that backbenchers, who have staged two unsuccessful attempted coups, would need heavyweight support from Cabinet ministers to succeed, and there is little sign of that at present. Some MPs believe the party will have a “final window of opportunity” to change its leader before the election after next month’s Pre-Budget Report.