Poll demand as Labour war erupts

As a leaked memo showed that Tony Blair had attacked his successor's "lamentable" performance as PM, close Blair ally Stephen Byers broke cover to accuse Mr Brown of lacking big ideas and call on Labour to "remake our case afresh".

Meanwhile, Foreign Secretary David Miliband came under fire for his newspaper article demanding "radical change" to give Labour a hope of winning the next election, seen by many as an effort to put himself in pole position to succeed Mr Brown.

Prominent backbencher Jon Cruddas - himself tipped as a possible centre-left leadership candidate if Mr Brown steps down - left no doubt he had Mr Miliband in mind when he condemned "unedifying behaviour by senior members of the party" indulging in "a narcissistic dash for personal glory".

Senior Cabinet ministers Chancellor Alistair Darling, Labour deputy leader Harriet Harman and Skills Secretary John Denham rallied to Mr Brown's defence with simultaneous articles in the News of the World saying he was the best man to lead the party into the next election.

And Mr Denham - who denied the ministers had co-ordinated their intervention - warned Mr Miliband he could let David Cameron's Tories win "by default" if he continued to fuel leadership speculation. "We need to be careful in the way we make our argument that we don't do things that inadvertently stop there being a good platform for Labour's case to come across," Mr Denham told Sky News. "David (Miliband) knows that."

Shadow cabinet minister Chris Grayling said: "The Labour Party is clearly split right down the middle with some people backing Brown and others trying to knife him.

"What we have is a government in chaos at a time when Britain faces serious challenges. We simply can't go on like this for another 18 months. We need a general election sooner rather than later."

In the memo, Mr Blair accused Brown of playing into the Conservatives' hands with a "lamentable" and "fatal" strategy of disowning the New Labour legacy of a decade in power.

The document emerged as close Blair ally Mr Byers told The Observer that Labour had "a mountain to climb" to win the next election, but had come forward with only "a multitude of small policies and worthy initiatives that are more suited to a Sunday afternoon stroll".