Labour's approval rating has slumped to 27 per cent after Gordon Brown's potentially endured one of his worst weeks as prime minister.
A ComRes poll for the Independent, taken in the wake of the HM Revenue and Customers (HMRC) data security breach and continued concerns over Northern Rock, shows support for the government has fallen six points over the past month.
David Cameron has failed to fully capitalise on this crisis of confidence, despite superficially opening up the Conservatives' largest poll lead since Margaret Thatcher's heyday.
The Conservatives have a 13 point lead about Labour. Their best result for 19 years, it echoes the 14-point lead enjoyed by Margaret Thatcher in a Times/Mori poll in 1988.
However, support for the Conservatives only just stands at the benchmark 40 per cent mark - seen as crucial for election success - and has fallen one point despite a highly-traumatic month for the government.
This suggests the Conservatives have not fully taken advantage of Gordon Brown's alleged incompetence, with voters not yet viewing Mr Cameron as a prime minister-in-waiting.
Despite this, Labour's poor rating means Mr Cameron could command a Commons majority of 64 seats.
Instead voters are abandoning Labour for the Liberal Democrats and other smaller parties.
Support for the Lib Dems is up two on 18 points, after falling to a low of 11 points in the wake of Menzies Campbell's resignation. Support for other parties is up four points on 14 per cent.
Although pollsters consistently point to a core anti-Tory vote blocking a surge in support for Mr Cameron, the results show the Conservatives are best at retaining their own core vote.
More than nine in ten 'natural Tories' say they intend to vote Conservative at the next election, compared to 78 per cent of natural Labour voters backing Mr Brown.
With the Liberal Democrat leadership contest ongoing, 70 per cent of 'natural' Lib Dems are planning to vote for the third party, with 17 per cent prepared to back Mr Cameron.
Nearly one in ten Labour supporters would now consider voting for the Tories.
Mr Brown plans to use this week to mount his political comeback and will face the media at his monthly press conference this morning.
An attempt yesterday to set out his policy vision to the Confederation of British Industry was overshadowed by the resignation of Labour general secretary Peter Watt over a fresh party funding scandal.