NICK Clegg last night made a bold pitch to become the next Prime Minister as he claimed the Liberal Democrats could leapfrog Labour and the Tories to win the next election.

In an ambitious speech to the party faithful, he said his was the only party capable of bringing "real change in Britain".

Seeking to counter the idea that Lib-Dems could never win power, he said sceptics who thought the party were not contenders should "think again".

"I want to be Prime Minister because I have spent half a lifetime imagining a better society, and I want to spend the next half making it happen," he said.

Aides to the Liberal Democrat leader confidently predicted he could defeat David Cameron's Conservatives and seize the keys to Number 10.

But privately some of his own MPs questioned the wisdom of outlining goals on such a grand scale, with one saying: "I rather suspect he won't be Prime Minister next year. Our ambitions should be more realistic."

To achieve the goal of becoming the first Liberal PM since Lloyd George, it would require the Lib-Dems to win more than 200 seats. For an overall majority they would need 300.

It would mean a substantial reversal in recent election performance for the party in Cornwall, Devon and Somerset, where Lib-Dem controlled councils have repeatedly fallen to the Tories. Until now, the party's strategy in the Westcountry had been to simply hang on to its 11 seats.

The boast of unprecedented electoral gains had echoes of David Steel's much-ridiculed Liberal conference speech in which he told activists to "go back to your constituencies, and prepare for government".

Party strategists insist there are enough undecided voters for the Lib-Dems to leapfrog both Labour and the Tories.

Mr Clegg heralded the "first day of the future of British politics" and called on voters to be "brave enough to make a fresh start". He said he had never thought there was an "easy route to power" but people were turning to the Lib-Dems' "pioneering spirit".

"Labour is dying on its feet. We are replacing them as the dominant force of progressive politics," he said.

"We are the alternative to a hollow Conservative Party that offers just an illusion of change."

In what was his last speech to an annual conference before the next election, Mr Clegg admitted many people do not regard the Lib Dems as "contenders" despite liking his policies. "I urge you to think again," he said.

The audacious claim to be heading for power came at the end of an awkward week for the party, where the conference has been dominated by unrest among delegates at the dropping of key pledges and concerns Vince Cable's treasury plans, including the so-called mansion tax, were unravelling.

Brushing aside the criticism, Mr Clegg asked voters to instead imagine Mr Cable as Chancellor "ushering in fairer taxes, cutting the banks down to size, tearing up the Treasury red tape that strangles local government".

He also talked about Yeovil MP David Laws soon being in the schools department as Education Secretary "throwing out" bureaucratic rules and Falmouth and Camborne MP Julia Goldsworthy cutting her Department for Local Government to half the size.

"There is hope for a different future, a different way of doing things in Britain, if we are brave enough to make a fresh start," Mr Clegg said. But the "Fantasy Cabinet" did not include mentions for North Devon MP Nick Harvey, the party's defence spokesman, or Taunton MP Jeremy Browne, who is Mr Cable's deputy in the finance team.

The Lib-Dems made great gains in the Westcountry in 1997, riding on the wave of anger at the Conservatives which swept Tony Blair's New Labour to power. Mr Clegg said voters who backed Labour then must realise the Lib-Dems "carry the torch of progress now". The alternative was "fake change from the Conservatives", he added.

Mr Clegg issued a blunt warning to activists that there was "no easy solution" on public spending given the dire state of public finances.

But after criticism of his cuts plans from even within his own frontbench team, he added: "I am not going to abandon our vision for a better Britain because money is tight."

He acknowledged there would be "difficult" decisions on spending but said: "Taking them is the price of fairness."

Mr Clegg also made a new promise to find work or training for young people within 90 days of them being made unemployed, using money raised from putting VAT back up to 17.5 per cent.

He restated his pledge to raise the starting threshold for income tax to £10,000 and warned the rich and polluters that they would foot the bill.

Mr Clegg was joined on stage by a number of Gurkha veterans as he raised his successful campaign earlier this year to ensure their citizenship rights.

He again urged Gordon Brown to take a different course in Afghanistan, saying that "time is running out". He also said a Lib-Dem government would put Britain "at the heart of the European Union".

Tory party chairman Eric Pickles said after Mr Clegg's speech he "still couldn't discover a reason for voters to choose him over David Cameron".