Sir Menzies Campbell will ditch the Liberal Democrats' policy of imposing a 50p top rate of tax on incomes of more than £100,000 if he becomes his party's leader.
He told The Independent would propose new "green" taxes on polluters to raise money for the Liberal Democrats' social objectives. His platform will be "fairer taxes, not higher taxes. Wealthy people and polluters should pay more; the poor and the old should pay less." He added: "I think we should use tax to promote opportunity, not to restrict ambition."
Sir Menzies backed moves by Vince Cable, the party's treasury spokes-man, to dump the 50p tax rate for other taxes such as property and capital gains taxes. "All of that is up for consideration," he said.
On the 50p rate, he said: "I don't think one should regard one particular part of the tax programme as if it were the Ark of the Covenant or the Holy Writ."
Green taxes would not mean a hike in petrol prices. "You do it by looking at how you can reward environmentally desirable activity and penalise activity which is undesirable," he said.
Today, flanked by a galaxy of the Liberal Democrats' rising stars, Sir Menzies, 64, will launch his campaign to succeed Charles Kennedy. He aims to turn his potential handicap to his advantage by offering a combination of his experience and the hunger for power among young turks such as Ed Davey, David Laws and Nick Clegg.
"My task is to ensure that talent gets a proper opportunity to flower," he said.
The former British athletics captain, who competed in the 1964 Olympics, said: "I see myself as a captain and a coach: to provide direction and to bring on this quite incredible talent. This energy and ability has got to be harnessed."
With David Cameron and Gordon Brown about to become new fathers again, does Sir Menzies feel age is more of an issue in today's televisual, presidential politics than it was 10 or 20 years ago? " I don't think my age will be any handicap," he replied. "More than half the electorate at the next election will be over 50. We are all working longer. The old retirement ages of 65 and 60 have to a large extent been overtaken by health and diet, people taking better care of themselves."
After suffering from cancer, Sir Menzies got a clean bill of health from doctors before Christmas. During his chemotherapy, he had gaps of two weeks between treatments rather than three because his doctors judged him "young and fit".
He acknowledged the need to show his party he is more than a safe pair of hands. He summarised his pitch to the party's 75,000 members as "authority, credibility, professionalism, passion, ambition and aspiration". Sir Menzies has a clear lead among the 62 Liberal Democrat MPs with more than 20 public pledges of support, more than his three rivals put together, and hopes to win the votes of half the MPs.
But the members will decide the contest. As acting leader, he used Mr Kennedy's office in the Commons to prepare for Prime Minister's Questions yesterday. But he will not move in because he is taking nothing for granted.
In his smaller Commons room after yesterday's joust, Sir Menzies was a relieved and relaxed man. A week earlier, a gaffe stalled his early momentum in the leadership election; he was distraught that his barrister's training let him down at a crucial moment.
He needed to do better yesterday and he did, putting Tony Blair on the defensive over sex offenders working in schools. "A week is a long time in politics," he said with a smile.
Could the anger among party members about the political assassination of Mr Kennedy harm his prospects? Revealingly, Sir Menzies urged party members to judge him on his record as an MP since 1987 rather than the traumatic events of the past six weeks.
"I feel very sorry for him [Mr Kennedy]. I recognise his very considerable talents." He said he was still on "good terms" with the man he has known since he was a fearsome 20-year-old student debater, and they spoke late last week.
"We had reached the point where, however we got there, he simply couldn't stay [as leader].
"For my part - one can never be certain of these things - I believe I did everything in my power to assist and support him."
He admitted he had "reservations" about Mr Kennedy's decision to go on the "stop the war" march before the Iraq conflict because it could have associate the party with anti-Americanism.
People who know him cannot believe he would ever keep the Tories in power. He described himself as a "centre-left politician", but recalled that the late John Smith, a long-standing friend, had berated him many times in the early hours for not joining Labour. A former Labour chief whip once offered him a safe seat.
Under the Tories, he could have become a High Court judge in 1996 but the late Roy Jenkins told him: "You still have a lot to offer here" and he stayed on at Westminster.
He now wants to prove Lord Jenkins right. "I have had three lives: in sport, the law and in politics. I have had a very full life. I have been very lucky to have it. I want to know why more people don't get that chance."Reuse content