As the fallout from the 10p tax row continued to dog the Prime Minister, he was under pressure to make way for a younger, more charismatic leader.

The belief that he should quit, among 55% of Labour voters, was revealed in a poll as he faced tough criticism from a former Cabinet colleague.

Ex-home secretary Charles Clarke attacked Mr Brown for using "dog whistle" tactics and complained that short-term errors were "eroding confidence in Labour's competence".

"We should finish with 'dog whistle' language, such as 'British jobs for British workers', which flatter some of the most chauvinistic and backward-looking parts of British society," Mr Clarke said.

"We should suspend the black arts of divisive inner-party briefing and bullying which penalise and inhibit debate and discussion about the future."

Mr Brown is also still under intense pressure to do more to reassure voters that they will not lose out from the abolition of the 10p income tax rate. Chancellor Alistair Darling promised Labour rebel Frank Field he was actively searching for all the "losers".

Mr Darling also said ministers were considering a whole range of measures to compensate them.

But Mr Field, and fellow Labour MP Greg Pope, kept up their demands that all help should be backdated to the beginning of April.

A Populus poll for The Times newspaper showed that support for Labour had plunged four points to 29% in the last month. Tories were up on 40%, giving David Cameron the biggest Tory lead in the five years of the Populus series of polls. The Liberal Democrats were up two points on 19%.