See Sir Menzies Campbell's career in pictures

Sir Menzies Campbell today dismissed speculation that he had been forced to quit as leader of the Liberal Democrats by the threat of rebellion within the party.

As the Lib Dems started the process of choosing his successor, Sir Menzies, 66, said in broadcast interviews tonight that he would have quashed any internal move to replace him. Instead, he blamed the media's obsession with his age for his abrupt departure.

The Lib Dem leader did not announce his own resignation last night, allowing Simon Hughes, the party president, and Vince Cable, deputy leader, to call an end to his leadership. But today Sir Menzies broke his silence.

“I had no sense that there were people wanting to move against me. If I had decided to go on and anyone had tried to move against me then I would have dealt with them pretty sharply,” he said. “This was my decision. I took this decision.”

Although he denied that rumbles of discontent had contributed to the decision, Sir Menzies admitted that the “cloying blanket” of criticism about his leadership was a factor. He said that in six interviews given at last month's party conference in Brighton, the issue of his leadership had come up in all of them.

Sir Menzies said he had become “irritated and frustrated” at the sniping and conceded that Gordon Brown's decision to rule out a snap election had contributed to his decision. With the next poll not now likely until 2009 the pressure for a younger leader would have intensified.

“There were seven consecutive days in which there were seven consecutive stories or reviews about my age and it became very clear to me it was going to be very hard to get out from under that,” he said suggesting that “such was the fixation on age we would not have been able” to pursue Lib Dem policies.

Meanwhile, the Liberal Democrats started the process of choosing their third party leader in less than two years. Nick Clegg, 40, the party’s home affairs spokesman, and the environment spokesman Chris Huhne, 53, who lost out to Sir Menzies 18 months ago, emerged as the immediate frontrunners.

Supporters of the former leader expressed dismay at the way he had been treated by fellow MPs - with one describing it as "absolutely despicable" - the Lib Dem front-bench tried to minimise the political damage by insisting that Sir Menzies had made the decision to resign without any pressure from the party.

Dr Cable, named interim leader last night, suggested that Sir Menzies had quit because he would have been too old to fight another election in 2009 or 2010, by which time he would have been 68 or 69. "If he had wanted to soldier on, we would have supported him. There is absolutely no question of plots," he said.

Paddy Ashdown, the party’s former leader, said that he had been due to meet Sir Menzies today and had been planning to tell him to stay as long as he felt was right.

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