A former Conservative minister has defected to Labour, warning that a victory for Michael Howard at the next election would be "dangerous".

Robert Jackson, the MP for Wantage in Oxfordshire, said he wanted Tony Blair to remain as prime minister.

His decision will come as a blow to the Tory leadership, which has been attempting to shift the focus on to its policies to cut government waste and lower taxes.

But the news was immediately welcomed by the prime minister, who said that under Howard's leadership the Conservatives were "drifting further rightwards".

The timing of the announcement is set to relieve the pressure on Labour, which has seen a damaging week of headlines focusing on the rift between Blair and chancellor Gordon Brown.

Jackson's verdict

Jackson, who had already announced his decision not to stand at the next election, told the Sunday Telegraph that a Conservative election victory would mean "certain harm".

The former education minister, who is on the pro-European wing of the party, said he could not "go quietly".

And announcing his decision in a letter to the local constituency chairman, Jackson listed a range of policies which he disagreed with.

"I have to ask myself whether the supposed wider benefits of a Conservative victory at the forthcoming election would outweigh the certain harm it would bring to institutions which matter greatly for their own sake, and for Britain's future as a knowledge-based society," he said.

He criticised the party for "envisaging tax cuts without any credible alternative policy for investment in the public services".

"While Labour policy for public service modernisation is moving in very promising directions, the Conservative Party's approach is mired in inextricable contradictions."

He also said the Conservatives had "developed an increasingly hostile attitude to Europe, which I believe would be damaging to our national interest if pursued in government".

"In the end 'my party right or wrong' cannot be the right attitude any more than the widely current view among Conservative MPs that 'we're not going to win anyway, so it doesn't matter'," he concluded.

"The simple fact is that in recent years the Conservative Party has been moving in the wrong direction, while the Labour Party has moved in the right direction."

Jackson said that he had come to "greatly admire Tony Blair's leadership of the country".

"He has risen above narrow sectional interests, and demonstrated real courage on both domestic reform and our country's international security."

Welcoming the move, the prime minister described Jackson as "a decent, fair-minded and dedicated public servant".

He predicted Jackson would be "warmly welcomed by Labour MPs and members".

"Like many people who used to be Conservatives, he now finds New Labour closer to one-nation politics than the present-day Conservative Party," Blair added.

"As he rightly says, they have learnt nothing from their two election defeats and are, if anything, drifting further rightwards.

"He offers a serious and measured analysis of where they are continuing to go wrong, and they would do well to listen."

Deputy prime minister John Prescott added that the move "is not just a rejection of the Tories but a positive endorsement of the government and the progress we are making for the country".