Why won't you talk to us?

First they were "Paxmanned", then they were "kebabbed", but now politicians are falling victim to an even more humiliating verb gaining popularity among broadcasters. It's called "empty-chairing", and, as you'd guess, involves an interviewer painfully addressing a vacant seat after yet another government department failed to supply a spokesman. For some unaccountable reason - a reputation for tough questions, perhaps? - presenters, from Jon Snow to Eddie Mair, are finding ministers ever less available. And, increasingly, they are allowing their frustration to show.

Last Sunday, for instance, Mair posed a number of tough questions about war plans against Iraq to Ben Bradshaw, the Foreign Office minister, on Radio 4's Broadcasting House. What was the Government's evidence against Iraq? How reliable was it? And why couldn't the public see it? Bradshaw, however, was not around to reply: an hour after the programme bid for Jack Straw or Bradshaw at 4pm on Friday, the Foreign Office's news department called to say that it would be impossible to supply either. So it was with some surprise that the programme received an e-mail from Bradshaw on Monday suggesting that he had never been told about the request, and would have gladly appeared.

Nor was this the first time that Bradshaw had been kept from listeners. Some months ago, he agreed to break a train journey to discuss the war in Afghanistan, but in the morning the Foreign Office told Radio 4 that he had become unavailable. Bradshaw, meanwhile, had been told by the Foreign Office's press handlers that the cancellation was actually Radio 4's decision after it dropped the item, according to a party to the negotiations.

"It's something listeners are increasingly cheesed off about, and they're keen to tell us," says Mair, who diplomatically puts last week-end's no-show down to "a mistake" at the Foreign Office. "Just the other week I got an e-mail suggesting that when they don't appear we should still list all the questions we would ask them. So we did that on Sunday." He accepts that diary clashes can hinder press officers' ability to meet every broadcaster's request, but worries that listeners are irritated by ministers who prove unavailable: "All this stuff about democracy and accountability is important, too."

Lack of availability is also an issue for Channel 4 News. "Politi-cians can be curiously scarce when there's a bad-news story around," notes Guy Ker, managing editor. "When they are unavailable, we let the viewer know by empty-chairing. The political process requires a bit more courage than politicians sometimes show."

A senior BBC editor insists the problem is at its worst for 20 years. "It is very, very much more difficult now than ever before. The lines which used to be drawn around ministers in trouble have been drawn ever more tightly. It's not just the Government - the Conservatives are so concerned that they'll make a mistake that they're not putting themselves forward either."

Yesterday, for instance, The World at One bid for Margaret Hodge at the education department to talk about the University for Industry's £1 million sponsorship of Who Wants to be a Millionaire? The programme was told that she was unavailable, but a short time later a separate press officer called to suggest a different interview about an Ofsted report on classroom assistants. "It's very clear that ministers were available, but the department was trying to control the agenda," says a frustrated Radio 4 source.

But the Today programme - which Tony Blair has ignored since the election campaign - faces the greatest tension with the New Labour spin machine. David Triesman, the party's general secretary, recently wrote: "I am now hard pushed to recall an instance where the Today programme, to choose an example, has dealt with a politician of any party as though he was not a consummate liar who was trying to line his own pocket."

John Humphrys finds these remarks "bizarre beyond belief". He says: "There's a lot of nonsense talked by party officials. I've written to Triesman asking him to refresh my memory, because I can't remember a single interview when we did treat a politician as a consummate liar. I've had no reply."

Humphrys insists that Today treats politicians with respect. "We don't brown-nose - we just ask the questions that listeners expect us to ask." Likewise, he finds that most politicians, apart from Blair, are happy to appear. "On Saturday's Today programme we didn't think we'd get a minister to talk about the smallpox vaccine story. But one was more than happy to come on."

"They all want to be on Today as it sets the news agenda," agrees a former Labour special adviser. Few programmes are favoured more than Jimmy Young on radio and Frost and GMTV on TV; Dimbleby and On the Record are notorious for "in-depth grilling". Newsnight "used to matter", says another exadviser, but is now second to Channel 4 News. The reason is more than ratings, he adds. "The minister can enjoy a glass of wine at dinner and not worry about how he sounds at 11pm."