He has monstered Michael Howard, and harangued Hazel Blears. And his tough- guy interview technique has made political interviews a spectator sport – two possible reasons why Jeremy Paxman may not get the chance to give Gordon Brown and David Cameron the once-over during the general election campaign.

Neither of the two party leaders seems in any rush to sign up for the Paxo treatment, even though invitations to the two men went out months ago.

It was hoped they would appear on Panorama, which intends to run separate interviews with the two men and Nick Clegg in half-hour specials starting next Monday. Clegg snapped up the invitation to be grilled by the Newsnight presenter, and he could be the first up next week.

But Cameron and Brown have been more coy. BBC sources said they had been asked to confirm by today whether they were taking part, but both failed to do so. The Tories, apparently, said they would only do it if Brown agreed. Brown's team have said he is still making his mind up. The Conservatives indicated today they were in no hurry to reply as they are busy preparing for the forthcoming TV debates, which start next Thursday.

However, BBC sources feel the party leaders will never turn the Paxman invitation down formally because of the fuss it would cause.

One insider said: "They are doing GMTV interviews, doing interviews with God knows who. On this they are running scared and using the TV debates as cover." Another added: "It is quite possible that one of the two big leaders will do it when it looks like they are behind in the polls, but right now it doesn't look likely."

The set-piece interviews have been game-changing moments in previous elections, with Paxman getting Tony Blair to say higher income tax voters would not be "clobbered" by a Labour government.

A BBC source said: "This is a tradition that dates back decades and they now risk being chucked away because of the TV debates. But what you'll see is that the TV debates will present the need for one-on-one TV interviews because their format will probably see them getting away with not answering the question."

Alistair Darling might bemoan the loss of the "one to one". In an interview in G2, the chancellor says: "I just sometimes wonder whether the viewers at home wouldn't get far more out of individuals being sat down and grilled for half an hour, an hour ... The interviewer's got to go from him to him to him ... and it can too often become a dingdong."