Lib Dems 'only alternative' - Clegg

As Gordon Brown faced further pressure to quit from some of his own MPs, Mr Clegg kicked off his first annual conference as party leader with a stinging assault on the major parties.

He faces a fight in Bournemouth this week to win the support of left-leaning activists for a pledge to slash public spending by £20 billion and for "big" tax cuts.

But he will tell them his "blueprint for a freer, fairer Britain" is the only way to show the Lib Dems understand voters' concerns during the present economic slowdown.

Talking to reporters as another Labour MP called for the PM to face a challenge, Mr Clegg said: "We are watching the death throes of the Labour Party. It's the end for Labour; I do not think there is any way back for them. They no longer stand for anything that the vast majority of British people need or want".

The Lib Dems were now "emerging as the only progressive party speaking up for people who want something different and something better", he insisted.

Addressing a rally of party members, he extended his attack to David Cameron's Tory Opposition.

"Here's a man who'll speak fondly of 'hardworking families' but has no actual plans to help them. A man who - with recession looming - puts millionaires first. A man who hopes that soundbites can fix the economy.

"If you want real solutions for Britain's economy are you really going to call this bunch of Conservative Cowboys? There's only one man who can be trusted with our economic future, and it's Vince Cable."

The nod to Mr Cable, the party's economics spokesman who proved a big hit as stand-in leader after last year's ousting of Sir Menzies Campbell, comes amid complaints from some in the party that Mr Clegg has failed to make enough of a mark since beating Chris Huhne for the top job in December.