Some Lib Dems have doubts over Sir Menzies' position Sir Menzies

He told BBC One's The Andrew Marr show his tax policies would help 90% of the population and the gap between rich and poor had become "too great".

The comments come after senior Lib Dem Lord Rodgers said some party members were "disappointed" with their leader.

But ahead of the Lib Dem annual conference in Brighton on Sunday, Sir Menzies said he will stay on as boss.

"I've made it perfectly clear... that I will lead the party into the next general election and into the next parliament," he said.

We are going for these people who have done the best of all out of the last 10 years Sir Menzies Campbell

He added that he was ready to fight an election, challenging Prime Minister Gordon Brown to "bring it on".

Of Labour's time in power, Sir Menzies said: "The people at the top have done very well. In fact, they've done too well.

"The division between rich and poor has become too great and it's time for it to be redressed."

Sir Menzies said his party's policy of replacing council tax with a local income tax would only leave those households earning more that �70,000 a year paying more.

'No mandate'

He criticised Gordon Brown's decision to abolish the lowest, 10p in the pound, rate of income tax in his last Budget as chancellor earlier this year.

This would leave households earning �18,500 a year, which did not receive tax credits, worse off, he added.

He said: "We are going for these people who have done the best of all out of the last 10 years."

Sir Menzies reiterated his party's policy to reduce the basic rate of income tax by 4p in the pound, saying this could be funded by increases in environmental taxes and changes to capital gains tax and tax relief on investments and pensions.

Vote on EU, say Lib Dems

He also said a Lib Dem government would offer a referendum on whether the UK stays in the European Union, rather than the vote demanded by Tories and trade unions on whether the country signs up to the EU treaty.

Sir Menzies has been Lib Dem leader since early 2006.

Earlier, Lord Rodgers told the BBC: "I think he's a very able man and an intelligent man and he's very good on foreign affairs, and I always want to listen to him and I respect what he's going to say.

"But he's had a very difficult task and some people are disappointed.

"There is a feeling that there's a lack of energy and an absence of direction, so I very much hope the conference will be different and change the mood really."

But Sir Menzies said the Lib Dems under him had "maintained a distinctive position in British politics". He added: "The great divisions are no longer between left and right but between liberal and authoritarian." The Lib Dem conference runs until Thursday.