In a New Year message he urged the party to take an "unparalleled opportunity" to win over millions more voters, setting May's local elections as an early test.

Mr Clegg, who narrowly beat Chris Huhne in the race to succeed Sir Menzies Campbell earlier this month, is the third man in as many New Years to head the party,

But he said he was the one to break the two-party stranglehold by tapping into Britain's natural liberal tendencies and promising to put people "in control of their destinies".

"We have before us an unparalleled opportunity. We must reach beyond the stale two-party system to the millions of people who share our liberal values and change Britain for the better," he said. "Let us show what that means in the local elections that face us this spring."

He said "putting British families back in control of their everyday lives" would be at the heart of his message - whether over ID cards, TV advertising aimed at children or flexible working.

"Giving power and responsibility to families - of every shape and size, of every background - is the only way to make sure everyone has a fair chance in life," he continued. "I believe no-one should be condemned by the circumstances of their birth. And I am certain that is what the British people believe, too.

"We are a nation with a strong sense of fair play, and natural justice. The challenge for our party is to persuade those people that their home is with the Liberal Democrats. We will do it by putting social mobility - a fair deal for every family - at the heart of our message."

He said he would campaign "relentlessly" for spending on pupils from the poorest backgrounds to be raised to the same level as in private schools and would cut taxes for low-income families. In a direct attack on David Cameron's Tories, who have deliberately tried to woo Lib Dem supporters with a liberal message, he said they wanted to "block opportunity not promote it".

Mr Clegg, who has said he is willing to be jailed rather than accept an ID card, concluded: "We should campaign tirelessly to stop the expensive, invasive and unnecessary identity cards scheme in its tracks.