Prime Minister David Cameron is refusing to take part in a head-to-head debate with the opposition leader Ed Miliband before the campaign for the general election.

Cameron's camp made what he described as a final offer to debate organizers, insisting the Conservative leader would sign up for a single 90-minute contest involving at least seven party leaders. Cameron's supporters are describing the single debate as the most fair.

The campaign chairman for the Liberal Democrats, Paddy Ashdown, said Thursday that Deputy Prime Minister Nick Clegg is prepared to step in and take part in a one-on-one contest to defend the coalition government's record.

Ashdown says if the "prime minister hasn't got the guts to stand up there and defend the record of this government, we'd be very happy to."