Broadcasters set out new proposals for TV debates ahead of the General Election and threatened to go ahead even if a party leader refuses to take part.
The TV companies are proposing two debates involving seven party leaders and a third face-off between David Cameron and Ed Miliband.
In a statement, the broadcasters said “the debates would take place with those who accepted the invitation”.
David Cameron has previously threatened not to take part if the Green Party is excluded from the debates, a move widely seen as an attempt to ensure Labour faces pressure from the Left as he comes under fire from the UK Independence Party on the Right.
The four major broadcasters today confirmed plans for a 7-7-2 format, under which two debates hosted by BBC and ITV would feature the leaders of Conservatives, Labour, Liberal Democrats, Ukip, the Greens, Scottish National Party and Plaid Cymru, and a third on Channel 4 and Sky would pit David Cameron against Ed Miliband in a head-to-head clash of the two men most likely to emerge as prime minister.
There was no immediate reaction from Mr Cameron but a Tory spokesman said the latest proposals were being “considered”.
The Liberal Democrats maintained their position that Nick Clegg should be allowed to take part in all the debates on the grounds that he should have the opportunity to defend the party’s record in Government from Labour attack.
The decision to involve the Greens, SNP and Plaid Cymru also drew criticism from Northern Ireland’s Democratic Unionist Party which outnumbers them all at Westminster.
Hinting that a legal challenge could be brought DUP leader Peter Robinson, Northern Ireland’s First Minister, said: “In light of the extension of the debates to smaller and regional parties, the failure of the broadcasters to invite the DUP to participate is inexplicable.”
Proposed dates for the debates are April 2, 16 and 30 - with the final clash coming exactly a week ahead of the May 7 poll.