David Cameron has finally agreed to appear in a single televised debate with six other party leaders on April 2 after weeks of political manoeuvrings,

But he is still refusing to go head-to-head with Ed Miliband. Labour said the latest offer from the Prime Minister was "one down, two to go".

Mr Cameron explained how the broadcasters had made him a formal offer of one seven-cornered debate but with two others, including the originally planned head-to-head with the Labour leader, dropped.

Labour made clear it was still working on the basis that three encounters were planned; Mr Miliband accused the Conservative leader of "going to any length to avoid a head-to-head debate".

However, the Liberal Democrats hailed the "latest proposals" from the broadcasters - which would also involve the main party leaders being interviewed separately on programmes alongside the single seven-way debate - as progress towards a "sensible solution".

Nicola Sturgeon, the SNP leader, noted: "While it is welcome David Cameron has accepted his position was indefensible and agreed to debate during the campaign period - abandoning his arrogant 'final offer' - he should sign up to the full programme of debates that is on the table."

The First Minister added: "I will debate David Cameron any time, anywhere, and on any number of occasions but a Tory Prime Minister simply cannot be allowed to dictate terms to everyone else."

Meantime, a Ukip spokesman said: "We agreed to the three debates the broadcasters proposed and will be turning up to the two we were invited to."

Previously, the broadcasters had mooted three debates with the first two on April 2 and 16, featuring Mr Cameron, Mr Miliband, Liberal Democrat leader Nick Clegg, Ms Sturgeon, Ukip's Nigel Farage, Green leader Natalie Bennett, and Plaid Cymru's Leanne Wood, followed by the head-to-head encounter on April 30 between the two men vying to be Prime Minister.

They had threatened to "empty chair" the Mr Cameron in any debate he failed to attend.

It is understood that a small group of TV executives have been in talks with the Conservatives since their leader insisted he would not back down on his "final offer" of a single debate to take place before the election campaign begins on March 30; it remains unclear whether other parties were involved.

Tory sources said the package of programmes agreed by the PM included an interview by Jeremy Paxman, featuring questions from a studio audience with Mr Miliband attending a similar event.

Then, on April 2, there would be a seven-way televised debate, including Mr Cameron and other party leaders.

A further "challengers' debate" would feature the leaders of the smaller parties.

On April 30, a week before polling day, Mr Cameron, Mr Miliband and Mr Clegg would take part in a rotating question time event, following one another into a television studio but not going head-to-head.

The PM said he agreed to do one TV debate at the weekend and challenged the other parties to agree, saying: "They have now got to stop running away from this and agree to the debate that the broadcasters have now suggested."

Asked if he was getting out of a head-to-head debate with Mr Miliband, he replied: "What I'm getting into is a set of television programmes and a televised debate."

But the Labour leader hit back, saying: "I'm fighting for the debate between me and David Cameron which the British people want.

"We now have the tawdry spectacle of the Prime Minister going to any length to avoid that debate."

He added: "I say to David Cameron, even at this late stage: agree to this debate which the British people deserve."