Gordon Brown is facing pressure from Labour MPs for a change in direction after a nightmare at the polls which saw the party slump to its worst results for a generation.
With results in from 98 councils in England and Wales, the BBC put Labour's projected national vote share at just 24%, trailing 20 points behind David Cameron's Conservatives on 44% and beaten into third place by the Liberal Democrats on 25%.
The margin was similar to the drubbing received by John Major in council elections in 1995, two years before he was ejected from Downing Street by Tony Blair.
Broadcasters' analysis suggested that the Tories would enjoy a landslide Commons majority of between 138 and 164 seats if the results were repeated in a general election.
Watching events unfold at Tory HQ, Mr Cameron told his Webcameron website the night was going "very well" for the party, which planted its flag in Labour's northern heartlands by seizing control of Bury and made a surprise gain in Southampton - one of the few Southern cities where Labour still has MPs.
Conservative local government spokesman Eric Pickles said the Tory successes meant Mr Brown would not risk calling a general election until the last possible date in 2010.
Labour MPs pointed the finger of blame for the bloodbath at the state of the economy and Mr Brown's decision to scrap the 10p rate of income tax, which hit millions of workers' pay packets in the weeks before the elections.
Ed Miliband, one of Mr Brown's key lieutenants, admitted the 10p issue had made the campaign "difficult" and the chairman of the Parliamentary Labour Party, Tony Lloyd, said it had hurt Labour on the doorstep.
Mr Lloyd said the electorate had sent a "very clear signal" to Labour in a "referendum on where the Government stands".
Cabinet minister John Denham, MP for Southampton Itchen, said Labour must listen to the concerns of voters in the South of England to restore its fortunes.