Mr Kennedy will speak at the party's Brighton conference

News of the speech, and recent poor opinion poll ratings, have led to talk Mr Kennedy may want to challenge his successor Sir Menzies Campbell.

On Sunday Mr Kennedy said the newspaper reports of him plotting was "fanciful".

But asked in The Independent if he may yet be leader again, he says: "Who knows what the future holds?"

In an e-mailed question and answer session with Independent readers Mr Kennedy adds: "Unpredictability is a central feature of political life."

Asked if he would like the chance to address the party's conference in September, Mr Kennedy says: "I am looking forward to giving a platform address at the party conference... I will be working on my speech during the summer recess."

Fairness

He also faces questions about how he feels "about the fact that your commitment to a 50p income tax band has been scrapped".

Mr Kennedy replies that "the key issue for me is the commitment to fairness and redistribution in tax policy overall" before warning "the policy is still to be decided at the conference".

It's up to me to maintain my good health - which I am - and in so doing I'm entitled to privacy Charles Kennedy Ex-Lib Dem leader

Mr Kennedy stepped down in January after a rebellion by many of his senior ministerial team and after admitting he had been battling a drink problem.

He is also asked when he last had an alcoholic drink.

He answers: "I made clear when I stepped down that I was in good health then and that remains the case. It's up to me to maintain my good health - which I am - and in so doing I'm entitled to privacy.

"So I see no need to go further than that save to say that my wife's support in all things is outstanding."

Mr Kennedy, due to front a 30 minute Channel 4 programme on politics on Friday, led the Lib Dems to their best general election result for 80 years, in 2005.

Asked about the party's recent poor opinion polls, he said that Lib Dems often outperform their opinion poll ratings, and praises the party's by-election performances in 2006.

'Shape-up' call

Sir Menzies, 65, has faced criticism of his performance as leader, particularly at prime minister's question time, since being elected as leader in March.

On Friday, he was told to "shape up" by a leading party member.

Liberal Democrat Welsh Assembly member Peter Black said Sir Menzies had made little impact with the public.

Earlier this year failed leadership contender Simon Hughes said Sir Menzies had until the conference to prove himself.

Two weeks ago, 53% of 1,000 people quizzed by ICM for BBC Two's Newsnight said Mr Kennedy would be the best leader of the party, compared with 26% for Sir Menzies.