Sir Menzies Campbell has insisted his position would not be undermined if he lost a vote on tax at his first party conference as Liberal Democrat leader.
Sir Menzies is hoping to win a vote on new tax proposals
Speaking as the conference began in Brighton, he told BBC News the vote was not a "High Noon" moment.
He wants to ditch the commitment to a 50p top rate on incomes more than £100,000 in favour of "green" taxes.
He also gave his strongest signal yet that he wants ex-leader Charles Kennedy back on the party's front bench.
The tax proposals are the biggest change in policy Sir Menzies has attempted since becoming leader earlier this year.
The plans include cutting 2p from the basic rate of income tax, with a £7bn increase in "green" taxes on cars and aviation used to fund the change.
Sir Menzies said: "If we are to fulfil the objective of substance and not symbolism the package as a whole should be adopted."
He told BBC One's Sunday AM programme the proposals were "redistributive" and would help take two million people out of paying tax altogether.
Former frontbencher Evan Harris is leading a challenge to the tax plans.
The MP has proposed an amendment calling for a system that is fairer "in relation to income as well as wealth", with a 50% rate on earnings over £150,000 per year.
But Sir Menzies said his leadership was not under question if he lost the vote.
"This is not High Noon," he said.
Sir Menzies said the conference would see "robust, full-blooded debates".
Mr Kennedy, who resigned as party leader after it emerged he had a drink problem, could still make a "remarkable contribution", he said.
The former leader is due to make a speech on the platform at the conference.
Mr Kennedy has said that talk of him challenging Sir Menzies for the leadership is fanciful, but has also said: "Who knows what the future holds?" when asked if he may yet become leader again.
Sir Menzies said he would welcome Mr Kennedy back onto the front bench "when he is ready".
"It would be madness for any leader not to have Charles Kennedy on the front bench because he has a rare quality in British politics in the early part of the 21st Century - he connects with the British people," he said.
Simon Hughes, who was a candidate in the leadership election, said earlier this year that Sir Menzies needed to be judged at the party conference.
Sir Menzies said he had found prime minister's questions "pretty torrid" but believed he had become "infinitely more comfortable" in the sessions.
But he said it was policy questions which really counted.
"If that is a test then I believe that is a task I have passed," he added.