Sir Menzies Campbell has said he feels "irritated and frustrated" over his resignation as leader of the Liberal Democrats.

Speaking to broadcasters on Tuesday amid speculation that he was forced to step down, Sir Menzies insisted he had made the decision by himself and said he acted in the interests of the party.

The 66-year-old told the BBC he was not sure he could escape the "cloying blanket" regarding his age and leadership ability.

He said: "I made my position clear. I always said I would lead from the front. I always said that decisions of this kind would be for me."

"I thought about this long and hard. And I reached the view, without too much difficulty, that the interests of the party certainly required that I step down, and step down now."

On a potential successor, Sir Menzies said he had "an idea" of who he wanted to win, but insisted he would support "the person that the party chooses".

"I want the person that emerges from what will no doubt be a very strenuous and robust leadership contest," he added.

Sir Menzies said he had ensured that the "brightest and the best talent in the party got every opportunity to strut its stuff - to show just how good it was".

"There are some very bright young men, and bright young women. Do not eliminate the possibility that a woman may stand in that election," he said.

Future

Asked whether he would be tempted to join Gordon Brown's government if invited to do so, the former leader refused to speculate on hypothetical questions.

The North East Fife MP said he wanted to stay in Parliament and stand in the next election "because politics for the last 20 years has essentially been my life".

"I would like to go on contributing," he added.

Referring to a serious illness five years ago, Sir Menzies said: "My philosophy is to regard every day as a bonus and as I've had three different lives: sport, the law, politics, and I've led my party. I have nothing to regret.

"To echo what John Major famously said: 'When it's time to leave the stage, leave the stage'."