Menzies Campbell admits that he will have his leadership ability put to the tax test at the Liberal Democrat's autumn conference.
In an interview set to be broadcast on the GMTV Sunday programme, the party leader will concede that his controversial tax plans may be met with opposition at the conference.
His tax plans, which have brought criticism from both the prime minister, Tony Blair, and shadow chancellor George Osborne propose a two pence cut in the basic rate, with the tax deficit supplemented by "green taxes" on vehicles and additional taxes for the rich.
"My aim is to cut the burden of direct taxes on the low paid and middle Britain and pay for it by raising taxes on those who pollute the environment and on the very wealthy," the party leader will say.
Environmental taxes would see both airlines and car drivers targeted with additional taxes, with claims that some vehicle owners could face road tax of over £2,000.
The Liberals have also dropped moves to tax top earners 50p in a pound.
"These [the tax proposals] will all be debated in full at the party conference and it's quite right the party conference could reject the idea of us no longer embracing a 50 pence top tax rate," he will say in Sunday's interview.
But Sir Menzies will say it is "essential" for people to know where he stands on the issue, and a debate will be both a professional and personal test for his leadership.