The Sun has said it will give Labour "the benefit of the doubt" and back Tony Blair's re-election bid.

Britain's top selling daily newspaper revealed on Wednesday night that it was backing Labour to win the election.

The news will come as a blow to the Conservatives, although the move was not unexpected.

Trevor Kavanagh, the paper's political editor, said Labour had "delivered their promise" on the economy.

But he cautioned: "There is no blank cheque in this endorsement."

"We assume that Tony Blair will carry out his pledge to carry out a full third term," he told Sky News.

The paper has "deep reservations" about some aspects of Labour's record, especially pensions, illegal asylum seekers, violent crime and the MRSA superbug.

Michael Howard was "raising the game of the Conservative Party", said Kavanagh.

"We've given the Labour Party the benefit of the doubt on this occasion and the main issues on which we have given them the benefit of the doubt is the handling of the economy and international relations," he added.