Support for Tony Blair has plummeted in the wake of allegations about his wife Cherie's financial dealings with conman Peter Foster, a new opinion poll suggests.

ICM/Guardian poll

Labour 41% Conservatives - 27% Liberal Democrats - 23% Others - 8%

But - in a blow for the Conservatives - the Labour Party itself has apparently escaped unscathed.

According to a poll by ICM in Tuesday's Guardian newspaper, Mr Blair's personal rating has fallen into negative territory for the first time since 2000's petrol crisis.

But Labour support has held steady at 41%, just one point less than last month.

The Tories, meanwhile, have sunk to their lowest rating in four years, at just 27%, with the Liberal Democrats, who traditionally lose support between general elections, just four points behind on 23%.

Increased majority

According to ICM, Mr Blair's personal rating currently stands at -1, with 45% of voters saying they are not happy with the job he is doing as prime minister.

This poll demonstrates yet again that the Conservatives are on the decline and seen by the public as a party out of touch and stuck in the past Mark Oaten Liberal Democrats

The poll also suggests damage to Mrs Blair's reputation, with 45% of voters saying they are unhappy with her explanation of recent events, compared with 35% when ICM asked the same question last Wednesday, after her emotional television address.

ICM interviewed a random sample of 1,006 adults by telephone between Friday 13 December and Monday 15 December.

Increased majority

Labour's apparently continuing popularity, despite the row over the Bristol flats, is a blow to Iain Duncan Smith.

The Tory leader has dismissed calls to stand down from senior figures in his own party, and is under pressure for a good showing in next May's local elections.

If a general election was held today, and people voted as suggested by the poll, Labour would be returned with an increased majority - and leading shadow cabinet members Oliver Letwin, Theresa May and David Davis would lose their seats to Lib Dems.

A Conservative spokesman said the party did not comment on individual polls.

Tory 'collapse'

The findings come as the Liberal Democrats step up their campaign to overtake the Tories as the main opposition party.

Lib Dem chairman Mark Oaten said: "This poll demonstrates yet again that the Conservatives are on the decline and seen by the public as a party out of touch and stuck in the past.

"The Liberal Democrats are more relevant and more likely to provide effective opposition to Labour on key issues like health, education, transport and crime."

Lib Dem leader Charles Kennedy is to meet senior party colleagues later on Tuesday to plot a strategy for next May's local elections.

They will also be discussing a strategy paper entitled The Strange Death of Tory England, Scotland and Wales, which predicts the collapse and eventual disappearance of the Conservative Party.

Shadow cabinet

The paper, by Lib Dem peer Lord Rennard, argues that the Tories may be "doomed as a political force" under Mr Duncan Smith.

Lord Rennard wants the party to redouble its efforts to target Tory marginals and, in particular, six seats held by members of the shadow cabinet.

The six are: Theresa May (Maidenhead, majority 3,284), Oliver Letwin (West Dorset, majority 1,414), David Davis (Haltempiece and Howden, majority 1,903), Tim Collins (Westmoreland and Lonsdale, majority 3,147) and Michael Howard (Folkestone and Hythe, majority 5,907).