British prime minister Gordon Brown is to subject himself to a grilling by Jeremy Paxman before the general election, his spokesman has said.

Lib Dem leader Nick Clegg's interview with the Newsnight presenter was aired last week. Brown will take part in a similar Panorama special on 26 April.

His Conservative counterpart, David Cameron, has yet to accept an invitation to take part in the series, although the Tories say negotiations continue.

A spokesman for Brown said: "Gordon has always said he's happy to answer any questions. He will be relishing the opportunity to debate the big choices facing the country."

Business secretary Peter Mandelson suggested Cameron was not keen to undergo a cross-examination by Paxman.

"David Cameron has so far refused to do the Paxman interview. We now know why. He doesn't like scrutiny and he doesn't like tough questions. The contrast with Gordon, who has agreed to do the Paxman interview, is obvious."

The interview with Cameron had been planned for this coming Monday but the Conservatives have asked the BBC for alternative dates.

A Conservative Party spokesman said: "We continue to talk to Panorama about the possibility of an inter- view."

Brown told supporters yesterday that the general election is "wide open" in the wake of the televised leaders' debate.

In a stump speech to party activists in Bedford, the prime minister said it was time to take the fight to Conservatives in key seats across the country.

He also said that, while the Lib Dems have gained an advantage from the TV debate, their policies will "unravel" as they and the Tories come under increasing scrutiny and pressure.

He said Labour should seek to exploit what it perceives as growing doubts about David Cameron's leadership fuelled by the ITV debate.

Meanwhile, foreign secretary David Miliband and defence secretary Bob Ainsworth launched Labour's defence and security manifesto, featuring further details on their commitment to the armed forces charter. They met veterans in south London.