Accepting the leadership of the Liberal Democrats, Nick Clegg has set out his ambition to create a "new politics".

Clegg told activists that his election as Lib Dem leader "marks a new beginning", characterised by "ambition and change".

"Renewed ambition for the Liberal Democrats, renewed ambition to reach out to millions of people who I know share our instincts and our values but don't yet vote for us," the former home affairs spokesman said.

Calling for the Lib Dems to become "more united" and "more ambitious", he said: "The challenge for my party is clear and simple.

"To define a liberal alternative to the discredited politics of big government.

"I want to open up my party, open up Westminster, open up politics for good.

"If you once voted for us but you think we've spent too much time focusing on ourselves. If you once voted for the Conservative Party but have no idea what they stand for any more. If you once voted for the Labour Party but feel let down by 10 years of disappointment.

"If you've given up voting altogether but still care about the world we live in, then a newly united, energetic and optimistic Liberal Democrat party is the party for you."

'Bright future'

Praising rival leadership contender Chris Huhne for his campaign, he pledged to work with the environment spokesman "for the sake of liberalism in Britain".

He also thanked deputy leader Vince Cable for his "spellbinding" leadership over the past two months, and said former leader Sir Menzies Campbell had restored "stability and professionalism".

Sir Menzies' work in building the Lib Dems had helped give the party a "bright future", Clegg said.

And he described Britain as "a place of "tolerance and pluralism" based on democracy and the rule of law.

"I'm a liberal - by temperament, by instinct, and by upbringing," Clegg said.

"I believe that liberalism is the thread that holds together everything that this country stands for. Pull out that thread and the fabric of our nation unravels."

The new leader claimed civil liberties had been "casually cast aside", arguing that "Britain is still not the liberal Britain we want it to be".

Politics has become "out of touch with people, out of touch with the modern world", said Clegg, adding: "That is why I have one single ambition.

"To change Britain to make it the liberal country I believe the British people want it to be."

Calling for a "new politics, a people's politics", he said: "Why have we stopped imagining a better society?

"I simply refuse to believe that the only alternative to a clapped-out Labour government is a Conservative Party that has no answers to the big issues.

"I want the Liberal Democrats to be the future of politics. Because Liberal Democrats have the courage to imagine a better society.

"I want today to mark the beginning of a real change in Britain. The beginning of Britain's liberal future."

'Admirably suited'

Announcing the result, Cable said either of the candidates would have been "admirably suited" to the top job.

And Huhne commended the new leader, saying: "I'm in no doubt at all that this is a great occasion for the Liberal Democrats".

The environment spokesman said he looked forward "to participating" as Clegg took the party "from strength the strength".

And praising Clegg for reaching out to younger people, he added: "This party is going to see even greater successes in the future than it has in the past".