Election 2015: Cameron agrees to just one TV debate
David Cameron has said he will take part in only one televised debate ahead of the general election, featuring seven party leaders.
The announcement rules out a head-to-head clash with Labour leader Ed Miliband ahead of the 7 May poll.
Downing Street said it was a "final offer" and criticised the "chaos" of the negotiating process.
Other parties criticised the PM, accusing him of "acting like a chicken" and trying to "bully" broadcasters.
BBC assistant political editor Norman Smith said: "Downing Street believes it is the fault of broadcasters, who they accuse of coming forward with proposals without consultation, to a timetable that was never going to be acceptable, and of failing to get the parties to get together for meaningful negotiations."
The broadcasters said they would respond to the Conservatives' proposal in due course.
'Held to ransom'
Under Mr Cameron's proposal, one 90-minute contest would take place before 30 March, when the official general election campaign is likely to start.
Downing Street said the Democratic Unionist Party should also be considered for inclusion.
It follows fierce debate over how the debates should be organised.
On Twitter, Liberal Democrat leader Nick Clegg told Mr Cameron people wanted the debates to go ahead and added: "Stop holding them to ransom by trying to dictate the terms."
Broadcasters have proposed a total of three debates.
The BBC and ITV were to hold two, both involving the Conservatives, Labour, Liberal Democrats, UKIP, Plaid Cymru, the SNP and the Greens.
A third debate - hosted by Sky and Channel 4 - would feature a head-to-head between Mr Cameron and Mr Miliband.
Labour's Douglas Alexander said his party still supported the broadcasters' plan and said Mr Cameron was "scared" of a debate with Mr Miliband.
"This is an outrageous attempt from the prime minister to bully the broadcasters into dropping their proposals for a head-to-head debate between David Cameron and Ed Miliband," he said.
A Liberal Democrat spokesman said it was "not right for one party to dictate their terms" over the debates.
"The Tories clearly do not want to discuss and debate the merits of their manifesto with the British public," he said.
"David Cameron and the Conservatives should stop thinking they can hold these debates to ransom."
A UKIP spokesman said: "After praising what a good thing debates were for democracy as recently as 2014, why is David Cameron now acting chicken and running as far away from them as possible?"
Sky and Channel 4 then offered to move the event to a different date if the leaders could agree.
In a joint statement, broadcasters said: "The BBC, ITV, Channel 4 and Sky have received an email from the prime minister's office with a proposal.
"The broadcasters are committed to providing our audiences with election debates.
"Twenty two million people watched the debates in 2010 and we believe the debates helped people to engage with the election.
"The broadcasters have set out their proposals and continue to talk to all the relevant parties on an equitable basis.
"We will respond to the Conservatives' proposal in due course."