Sources say prime minister vetoed Lib Dem leader’s participation in third event because he did not want to be only absentee

David Cameron has blocked Nick Clegg from appearing in a general election TV debate three weeks before polling day because he doesn’t want to be the only absent leader, it has been claimed.

After months of wrangling over the composition, format and timing of the debates, the BBC, ITV, Sky and Channel 4 announced the final deal with the political parties on Saturday. The first event in advance of the 7 May general election will be on Sky News and Channel 4 this Thursday, when the prime minister and the Labour leader, Ed Miliband, will be interviewed separately by Jeremy Paxman and then answer questions from a studio audience.

On 2 April Cameron will join Miliband, Clegg and the leaders of Ukip (Nigel Farage), the SNP (Nicola Sturgeon), the Greens (Natalie Bennett) and Plaid Cymru (Leanne Wood) in a seven-way ITV debate moderated by Julie Etchingham.

Cameron, who says the 2010 TV debates “sucked the life” out of the campaign, has insisted he will only appear in one event alongside other leaders and rejected calls from Miliband for a head-to-head. This has led to claims that he is running scared of his opponents and does not want to defend the government’s record.

On Saturday sources close to the negotiations said Cameron and his team had prevented Clegg from appearing in the third televised event on 16 April with five other party leaders, because he did not want to be the only absent leader and because he did not want Clegg to speak on behalf of the government. A Lib Dem spokesman made it clear that Clegg was not happy at being left off the list for the BBC debate, moderated by David Dimbleby, saying the party had “strong objections to being excluded from any TV debate or interview”.

A spokesman said: “If it was down to us, we would be in every TV debate and every interview. But we think the politicians and broadcasters have ducked and dived long enough and just need to get on with it now and ensure the public have the opportunity, however flawed the format, to scrutinise their politicians.”

The Tories claimed it was the broadcasters’ idea to keep Clegg out of the “challengers” debate and not the result of their demands.

The final encounter will be a special Question Time on BBC1 on 30 April featuring Cameron, Miliband and Clegg answering questions separately from a studio audience.

A joint statement from the broadcasters said: “We’re delighted that there will be a debate with all the party leaders during the election campaign. The debate on 2 April will build on the success of the 2010 TV debates which were so highly valued by viewers.”

A Labour source said: “The cowardice of David Cameron is still preventing the head-to-head with Ed Miliband. Cameron is now in the ludicrous position of saying he will attend the same programme and take the same questions from the same audience as Ed Miliband but will not debate him face to face.”