Mark Oaten today withdrew from the race to succeed Charles Kennedy as leader of the Liberal Democrats after admitting that he did not have enough parliamentary support.

Mr Oaten said that he had stood for the leadership because he had a "vision" for the future and had received strong support from activists and Liberal Democrat members around the country.

"But what has become very clear over the last few days is that that support is not matched by my colleagues in parliament," he told reporters.

"It’s become clear to me that I cannot get a level of support amongst members of parliament that I think is necessary if you are going to lead this party."

Rival camps had been predicting privately for some days that Mr Oaten would be forced to pull out after the entry into the race of Chris Huhne, a former journalist who arrived in the Commons only in May last year, pushed him into fourth place.

Mr Oaten had presented himself as a young moderniser, in contrast with Sir Menzies Campbell, the 64-year-old frontrunner. But his campaign failed to spark into life, and he was seen to be trailing behind Sir Menzies, Simon Hughes, the party president, and Mr Huhne.

Only one MP, Lembit Opik - his campaign manager - and one peer, Baroness Ludford, actually supported his bid.

Although Mr Oaten was able to find seven MPs to nominate him to stand, the other six made clear that they were doing so only to enable party members to have a choice of candidates. Nominations close next Wednesday.

It is understood that the final straw was the leaking yesterday of an e-mail to Mr Oaten from Charles Kennedy’s chief aide, Anna Werrin, telling how the former leader had asked fellow MPs Mike Hancock, Paul Keetch and Paul Rowen to nominate him. Another who was approached in this way, David Heath, declined to do so.

Although Mr Oaten called in police to investigate, saying the e-mail must have been stolen from his office, Ms Werrin accused Mr Oaten’s own campaign of leaking it to imply he had the backing of Charles Kennedy - which, she said, was not the case.

Today Mr Oaten referred obliquely to the situation, saying that he had wanted a "positive" campaign, and did not want to be part of a process in which private conversations were leaked. Formally announcing his decision outside the House of Commons, he said he would be spending the weekend relaxing with his family while he decided his future.

His withdrawal came an hour after Sir Menzies Campbell officially launched his leadership bid in a Westminster restaurant. By contrast, the veteran Lib Dem foreign affairs spokesman said that he had been overwhelmed by support for his campaign.

SIr Menzies told reporters and supporters that the removal vans may not yet have arrived at Downing Street, but that "the house of Blair" would not be here for much longer. He claimed that he was ready to go head-to-head with Gordon Brown and David Cameron.

"Under my leadership the Liberal Democrats would not be making polite interjections from the sidelines, we would be hammering on the doors of power," he promised.

Sir Menzies said that it was his mission to harness the party’s abilities to ensure the Liberal Democrats and their ideas were the rallying point for the new political era.

He confronted the criticism that at 64 he is too old to lead a national party, claiming that he was now even more determined than when he entered politics in 1970, and more energised than when he became an MP in 1987.

He has denied that he would be a mere caretaker leader. But opponents are likely seize on his promise today to be "a bridge to the future" as evidence he would not be a long-term leader.

He will unveil his manifesto next week, and is expected to single out the environment, civil liberties and the war on poverty as his flagship issues.

Sir Menzies was surrounded by supporters for the launch, aimed at emphasising his appeal to younger elements in the party. Britain’s youngest MP, Jo Swinson, 25, praised his "unique blend of statesmanship, warmth and determination to win". She said he had the stature and experience to take on Mr Blair and Mr Brown.

Nick Clegg, who has himself been tipped as a future leader, said that Sir Menzies had a remarkable ability to motivate his team and deliver "the best possible results" for the Lib Dems.

Veteran Lib Dem Baroness Williams hailed him as a man who would stick to his principles. And she said his foreign affairs expertise would be invaluable given the inexperience of Mr Brown and Mr Cameron in world affairs. "He is the man the Liberal Democrats need, he is the man Parliament needs and he is the man the country needs," she said.

The leadership contest will be decided by a postal ballot of the party's 73,000 members. The new Lib Dem leader will be named on 2 March, a day before the party's spring conference opens in Harrogate.

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