SIR Menzies Campbell said his age could be a vote-winner for the Liberal Democrats as he tackled the issue head-on at the party's conference yesterday.

The Lib Dem leader - put on the spot during a question-and-answer session - said politics was "not so much about age, it's about judgement and experience".

And he joked: "I know age is a real problem, but I promise not to take advantage of the youth and inexperience of my opponents."

The quip came after renewed mutterings by some Lib Dems about their 66-year-old leader.

Sir Menzies also accused Gordon Brown of performing a "great tease" on the British public about a possible snap election next month. He said the past four weeks, during which the Prime Minister has refused to rule out an October poll, made the argument for fixed, four-year parliaments.

And he repeated his call for Mr Brown to seek his own mandate to govern the country, adding: "We are ready. Bring it on."

The question about his age - the issue that has dogged Sir Menzies' leadership - was immediately seen as an attempt to silence his critic.

He also used his first appearance of the week on the conference platform in Brighton to denounce Tory leader David Cameron for his "ludicrous" claim that Britain was "in a state of anarchy".

And he urged his party not to let old prejudices stand in the way of increasing its number of women MPs. There are only nine out of 63 MPs. But Sir Menzies slipped up when he referred to the economic challenge posed by "Italy and China", later correcting himself by saying "India".

He delighted the sketchwriters by admitting he was "scared stiff" before big Commons occasions and by joking, at one point "Well, of course I'm a failure".

Earlier, former leader Charles Kennedy was asked in a radio interview whether the political climate was tougher for Sir Menzies. Mr Kennedy said: "No, I don't think so. There's nothing that has come as a surprise."

Last night, Sir Menzies also faced a challenge to his insistence that there is no need for a referendum on the proposed European Union reform treaty.

A group of 34 Lib Dem councillors released an open letter insisting the treaty was essentially the same as the aborted EU constitution on which the Lib Dems demanded a poll.

The 34 included three councillors from Redcar and Cleveland, Irene Curr, Eric Empson and Margaret Wilson.

Mike Hancock, a Lib Dem MP, said: "This letter reflects much wider feeling in the party. Many people in the grass roots think we should be putting pressure on the Government to keep its promise."