Gordon Brown looked increasingly beleaguered yesterday after a fourth UK government minister resigned in 24 hours.

When Mr Brown took over as the prime minister from Tony Blair in June 2007, opinion polls gave their Labour party its biggest lead over the opposition Conservative party since before the 2003 invasion of Iraq.

But the lead evaporated in October when, after weeks of speculation, Mr Brown ruled out an early election. Analysts saw his indecision as the beginning of his descent in popularity. By late last year Mr Brown's handling of the financial crisis seemed to be reviving Labour's political fortunes but in March they took a serious knock when the home secretary, already under investigation over her expenses, was forced to apologised for using public money to pay for adult films watched by her husband.