The Conservative Party has opened up a unexpected six point lead over Labour, according to a poll published on Monday afternoon.
The survey conducted by pollster Lord Ashcroft put the Tories on 34%, ahead of Labour on 28%. The poll Lib Dems placed Ukip on 16% and the Lib Dems and Greens tied on 8%.
The result will give a boost to David Cameron, who today set out his key themes for the long four month election campaign ahead.
However Labour will draw comfort from a separate poll published today that showed almost the exact opposite result. A Populus survey put Labour's support at 37% compared to 32% for the Tories - a five point lead for Ed Miliband.
Lord Ashcroft Poll
CONSERVATIVES - 34 (+4)
LABOUR - 28 (-3)
LIB DEM - 8 (0)
UKIP - 16 (-3)
GREEN - 8 (+3)
CONSERVATIVES - 32 (-1)
LABOUR - 37 (+3)
LIB DEM - 10 (+2)
UKIP - 13 (-1)
OTHER - 8 (-3)
In his analysis of the poll, Ashcroft cautions that the 3% margin of error could mean the Tories and Labour are actually tied on 31%. However he said the numbers could represent the "start of a shift in opinion as the choice looms larger at the start of an election year".
Cameron has insisted Miliband and Nick Clegg are "running away" from TV debates in the run-up to the general election - despite his own refusal to take part unless the Greens are represented.
The prime minister has ruled out appearing in the debates under the current format proposed by the broadcasters, which would see Ukip's Nigel Farage take part but not Green leader Natalie Bennett.
Miliband said broadcasters should "empty-chair" Cameron if he refuses to appear in televised leaders' debates ahead of the May 7 general election, while former Tory chairman Lord Tebbit warned that voters will conclude Cameron is "frit" if he dodges the live TV showdowns.
Asked about his opposition to the format proposed by broadcasters, Cameron said: "I don't want to pass up the opportunity of talking to millions of people about these vital issues.
"I think the debates were successful last time, I think they were good and I would like them to happen again.
"But we have got to have a proper set of rules. It seems to me that if people want one minor party - Ukip - to be involved, you can't exclude another minor party, the Greens.
"So I have made, I think, a perfectly reasonable point, which is if you are going to have one, you had better have the other."
Under plans put forward by the major broadcasters last year, the Prime Minister would take on Miliband alone in one debate, with another featuring the three mainstream party leaders and a third also including Farage.
Speaking at an event in Nottingham, Cameron suggested it was Labour and the Liberal Democrats who were standing in the way of the Green leader being invited to take part in a debate.
He said: "I can quite understand why Labour and the Liberal Democrats are running away from this because they see the Greens as a threat to them. Well, tough.
"They beat the Liberals in the European elections, they have got a Member of Parliament. I don't see any logical argument for excluding the Greens if you are going to include Ukip."