Sir Alan said "leading reform" would be the task of the next speaker
Veteran Lib Dem Sir Alan Beith has become the first MP to declare an interest in replacing Michael Martin as House of Commons Speaker.
Sir Alan, who was in the running for the post in 2000, told BBC News he would stand if he had enough support.
He added that he had "started to get indications of that from people in at least three parties".
Earlier, Mr Martin announced he would stand down amid pressure over his handling of MPs expenses.
He told the Commons he would relinquish his post on 21 June, allowing MPs to choose his successor the following day.
'Whiter than white'
Sir Alan, MP for Berwick Upon Tweed since 1973, said he was "willing to take on the task of leading reform" as speaker.
He told the BBC: "Over a period of time, even before recent events, various people have encouraged me to stand when the opportunity arose and I listened to that advice.
"But I think it's very important now that the House of Commons has a Speaker who actually leads on reform rather than simply feeling that the job of the Speaker is to defend the House of Commons as it is."
Sir Alan added that he cared deeply about making the House of Commons acceptable to the British public as the "core of our democracy".
Asked whether he was "whiter than white", he joked: "Nobody is whiter than white."
Chairman of the Commons constitutional affairs committee, Sir Alan was a candidate for the Lib Dem party leadership in 1987.
Although his interview made him the first MP to express an interest in the post, a number of candidates have already been suggested as front-runners.
They include Tory grandee Sir George Young, Deputy Speaker Sir Alan Haselhurst, independent-minded Labour MPs Frank Field and Chris Mullin and Sir Alan's former party leader Sir Menzies Campbell.