Latest Opinium/Observer poll shows 51% of voters believe David Cameron is looking for excuses not to take part in TV debate

Labour has a five-point lead over the Conservatives in the latest Opinium/Observer poll, which shows that half of voters think the prime minister is looking for excuses not to take part in live television debates ahead of the 7 May general election.

Ed Miliband’s party has held steady on 33% – the same score as the previous poll two weeks ago – while the Conservatives have fallen by four points to 28%.

Nigel Farage’s Ukip has enjoyed a three-point bounce and is up to 20%, while the Liberal Democrats are down one on 7% and the Greens up two on 6%. The SNP is up one point on 5%.

The gap between the approval ratings of Cameron and Miliband has also narrowed slightly with Cameron down three points to -11% – when those who disapprove of his performance are subtracted from those who approve – while Miliband’s rating has stayed steady on -29%.

Opinium Research carried out an online survey of 1,966 British adults aged 18 and over, from 13 to 16 January 2015. Results have been weighted to nationally representative criteria.

They asked a series of questions about television debates after David Cameron made clear he would not take part unless the Greens were invited, on the grounds that it would be unfair to ask Ukip without inviting other small parties.

Some 51% of voters – including 32% of Conservatives – think that the prime minister is looking for excuses not to take part, against 40% of Tory supporters who think he is right not to take part without the Greens.

Although Cameron has said he is still open to the idea of televised debates if the Greens are admitted and the right formula can be found, Tory strategists are adamant that he will not do so.

They fear that giving Farage equal status to the prime minister on stage will allow him a platform from which he could well put on a populist performance that will boost his ratings. They also fear that Ed Miliband could do better than expected allowing him to recover ground in personal ratings and boost his credibility as a potential prime minister.

The Tories believe that although the public will not think well of the prime minister for refusing to take part, that the damage to him from not doing so will be limited, and less, potentially, than the gains for his rivals.

Asked who they think would perform well in television debates, 49% said Nigel Farage , 42% David Cameron, while 33% named Natalie Bennett, the leader of the Greens, 27% Ed Miliband and just 22% Nick Clegg.

Amost four out of five voters (79%) think the television debates should go ahead though slightly fewer, 77% think they actually will.