Mr Brown's Labour Party, reeling from a crushing defeat in the Glasgow East by-election, plunged into further disarray on Friday night as MPs and union leaders called for a leadership challenge, the Times of London reported.

Senior ministers blamed the loss of the party's 25th safest seat on rises in the cost of living. In private, however, most were preparing to confront Mr Brown in September after the summer recess, if Labour's poll ratings do not improve to at least 30per cent.

Justice Secretary Jack Straw will be asked to tell Mr Brown to go, one Cabinet minister told the Times. If he refuses, others are prepared to lead the coup.

Delegates are scheduled to meet in September for the governing Labour Party's annual conference, and some have hinted that Mr Brown should resign before the next general election.

'We need a new start and that can only come from a debate around the leadership. I hope those discussions will take place,' said Mr Graham Stringer, a Labour lawmaker.

Labour Whips have reported that the possible candidates to replace Mr Brown - including Foreign Secretary David Miliband, Work and Pensions Secretary James Purnell and Health Secretary Alan Johnson - are already being wooed by MPs, the Times said.

The Labour Party's popularity has waned, due to a backlash over the unpopular Iraq war and mounting economic woes confronting Mr Brown.

The loss in Glasgow East, a seat held by Labour for over 50 years, was the third by-election blow for Labour in as many months.

In May, Labour lost the safe seat of Crewe and Nantwich to the opposition Conservative Party. Then the following month, it limped home in fifth place in the Henley by-election with a much reduced 3.1per cent of the vote.

Labour's current poll rating averages 26per cent, as opposed to 46per cent for Conservatives.

'No party has come back from below 30per cent to win the next election,' poll expert John Curtis, of Strathclyde University, told the Times. He said it was not impossible for Mr Brown to engineer a return to 30per cent, but added that such a figure was a minimum requirement.

Mr Brown, meanwhile, barely concealed his plea for time. At a national policy forum meeting in Warwick on Friday, he urged the party to 'have confidence' in policies which he said would 'persuade' voters to back the party at the next general election.

He won the support of his most likely successor, Mr Miliband, who called on the party to focus on the issues that concern voters - jobs, housing and anti-social behaviour.

AP