I'm here to stay, says Campbell

While he admitted that the party's poll ratings were not as high as he would like, Sir Menzies insisted he had successfully maintained its "distinctive position" as the "real opposition" in British politics.

"I've made it clear I will lead the party through this parliament, into the general election, and into the parliament beyond," he told BBC1's Sunday AM.

"Nobody should be in any doubt about that, in television studios or elsewhere."

Sir Menzies issued his defiant message as Lord Rogers, the former Lib Dem leader in the upper house, expressed "disappointment" at his performance and voiced fears that the party was "suffering a lack of energy and an absence of direction".

Two separate polls also suggested that a significant minority of local constituency association chairmen were not confident Sir Menzies was taking them in the right direction, and indicated that his approval ratings with the wider electorate were lagging far behind those of the other two main party leaders.

However, the Lib Dems Home Affairs spokesman Nick Clegg - touted in many quarters as a replacement for Sir Menzies - sprang to his defence, telling GMTV: "I am absolutely certain that Ming - because he said it to me, he said it to lots of people and he said it publicly - that he will and wishes to lead this party...up to and through and beyond the next general election, and I fully, fully, fully support him in doing that.

"I think people have got, frankly, short memories. I think they forget that 18 months ago or so the Liberal Democrats went through an extraordinarily turbulent period, very, very difficult."

Mr Clegg added that Sir Menzies had "calmed" and renewed the party since Charles Kennedy resigned after admitting he had sought treatment for alcoholism.

"I think it would be foolish in the extreme for anyone within the Liberal Democrats to start raising serious question marks about Ming's performance, which I think has been excellent."