DEPUTY Prime Minister Nick Clegg has called on broadcasters to show some "backbone" and hold the general election leaders' debates without David Cameron.

The Tory leader has threatened to boycott the highly-anticipated televised showdowns if the Green party is not included.

But opponents have accused him of political opportunism and claim his new-found interest in the Greens is a ruse to duck the debates.

Liberal Democrat leader Mr Clegg urged television companies to press ahead and 'empty chair' the Prime Minister.

Such a move could keep alive hopes of a multi-party debate, for which the SNP is also pressing for a place.

No 10 suggested earlier this week that Mr Cameron could be prepared to back down - but only to take part in a straight head-to-head with Labour leader Ed Miliband.

Mr Clegg accused the Tory leader of simply offering "excuses" about why he does not want to appear in a wider debate.

Some senior Tories blame the 2010 leaders' debates - and, more specifically, the participation of the Lib Dems - for Mr Cameron losing that election.

Mr Clegg was the unexpected star, spawning the catchphrase "I agree with Nick" and briefly sending his party soaring in the polls.

The electoral fortunes of the Lib Dems may have plummeted since then but many Conservatives still feel another round of TV debates is too risky, especially as broadcasters have included the Ukip leader Nigel Farage.

A new poll highlights what they see as the potential risk.

The survey found that almost half of voters think Mr Farage is 'saying what people think'.

Mr Clegg he was unhappy with parts of the proposed format of the debates, but said that the Conservative leader "has put himself in an unsustainable, laughable position" with "see-through" excuses.

"He'd save himself a lot of anguish just to accept the basic principles," Mr Clegg said. "It's not up to anybody to decide how the debates take place."

He called on the broadcasters to "develop a bit of backbone", saying they should not be "bullied" by the Conservatives.