Jack Straw has insisted he is "absolutely convinced" Gordon Brown should remain as Prime Minister.

The Justice Secretary issued a public warning to MPs that it would be a "big mistake" to plot to remove Mr Brown, following reports of an autumn coup.

Last week's catastrophic by-election defeat by the SNP in Glasgow East has intensified speculation Mr Brown could be forced out in a bid to reverse the Government's plummeting popularity.

But Mr Straw said: "I am absolutely convinced that Gordon Brown is the right man to be leading the Labour Party.

"The result in Glasgow East was obviously disappointing but it would be a big mistake for the Labour Party to now turn in on itself and indulge in a summer of introspection.

"We must instead focus relentlessly on the issues which matter most to people, listen to their concerns and work hard to address them."

He added: "Gordon Brown is the best leader to lead us through these tough times. He has done so before and he will do so again."

Several newspapers have reported that George Howarth, a former minister and a close ally of Mr Straw, is gathering support for a move against Mr Brown in the autumn.

But Mr Howarth said: "Jack is not up to anything. If anyone thinks I am collecting names for him, they are mistaken."

Labour's deputy leader Harriet Harman also backed Mr Brown, saying: "What's in the best interests of the country is that we have a strong and experienced Prime Minister who's been one of the foremost finance ministers of the world over the last ten years."

A new opinion poll shows Labour trailing in third place among voters in the Tories' top 30 target constituencies.

The CrosbyTextor survey saw Labour slump to just 17 per cent - 24 behind the Tories and one worse off than the Liberal Democrats.

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