Brown tells the plotters: Unite or you'll fail nation

The Prime Minister stepped up his fight-back as ministers and activists began gathering in Manchester for an annual party conference that could make or break his leadership.

"We are a team," he said. "We are working together, we have a common purpose. We would fail the country if we did not discharge that purpose as a group of people working together and doing so in a very disciplined way and that is what I intend to continue doing."

His comments in a Sky News interview being broadcast tonight come after members of the Cabinet, including James Purnell and John Hutton, refused to condemn MPs openly calling for a change of leadership. A straw poll of Labour supporters today claimed that more than half - 54 per cent - would prefer a new leader for the next election. The survey by LabourHome.com found 45 per cent thought a change would improve the party's chances of winning. Almost six in 10 thought the Manchester conference should vote on whether to subject Mr Brown to a contest.

Although not a scientific poll, the survey will raise fears that party activists are losing confidence in Mr Brown. The website is popular among young Labour activists although the 788 respondents were self-selected.

Mr Brown was boosted today by support from Jon Cruddas, the Dagenham MP who is expected to stand as a centre-Left successor when Mr Brown leaves office.

A grassroots favourite, he criticised calls for a leadership contest and signalled he would accept a job in a reshuffle. "It's all hands to the pump now," he said in an interview with The Times.

Mr Brown has decided to put his personal handling of the economic crisis at the centre of his fight-back. His strategy to beat Mr Cameron, say insiders, is to tough out the economic slowdown and show he has a fairer vision for the future.

It was revealed that the backdrop to his conference speech will be the slogan "Winning the Fight for Britain's Future".

"This not the time for faint-hearts," Mr Brown told Sky. "This is the time for people who know how to deal with difficult economic circumstances." Ministers think Mr Brown may have turned a corner when he came out fighting yesterday by pledging to "clean up the system" in the City, shortly before watchdogs banned shortselling of struggling banks.

Mr Brown said he was prepared to tough out a period of unpopularity - making clear to rebels that he will not relinquish the leadership voluntarily. "You go through periods, sometimes you are popular, sometimes people resent the decisions you make and sometimes people are disappointed," he said. "You always get that. You take the rough with the smooth. You deal with the problems you face."

Labour was rattled this week by a Mori poll showing the party 28 points behind David Cameron's Tories. But Harriet Harman said a leadership contest would be "completely wrong".