Media lawyers today dismissed warnings by Peter Hain, the Welsh Secretary, that the BBC could face legal action unless it cancelled an appearance on Question Time by the leader of the British National Party.

Mr Hain said the far-right party had effectively been ruled unlawful since agreeing to amend its constitution after a court order last week and should therefore be barred from the programme

The former anti-Apartheid campaigner claimed that the BBC would face a legal challenge if it pressed ahead with plans to allow the “illegal” BNP a seat on the political panel show.

Tony Ballard, of Harbottle Lewis, a firm of specialist media lawyers, said: “There is no foundation for such a case. Anyone wishing to challenge the BBC would face great difficulty. I think the BBC’s position would be unassailable.”

Mr Griffin, who will be on the Question Time panel on Thursday, has accepted that the BNP must suspend the enrolment of new members until it had abolished its whites-only membership rules to meet discrimination legislation.

But Mr Ballard said it was irrelevant. “The legality of the party would have no bearing whatsoever,” he said. “I don’t think a challenge would have much hope of even getting leave to apply to the High Court.”

In a letter to Mark Thompson, the BBC Director-General, Mr Hain wrote: “Now that the BNP have accepted they are at present an unlawful body, it would be perverse of you to maintain that they are just like any other democratically-elected party.

“If you do not review the decision you may run the very serious risk of legal challenge in addition to the moral objections that I make. In my view, your approach is unreasonable, irrational and unlawful.”

A media lawyer who wished to remain anonymous claimed that Mr Hain had made two unfounded leaps of faith. Firstly, by suggesting that the BNP was in any way an illegal party and secondly by suggesting that the BBC would be prevented from inviting them on even if the party was in some way unlawful.

“It’s complete nonsense,” he said. “I think it’s pretty shocking that a Minister of State would make such an assertion.”

During the 1980s, Margaret Thatcher was able to limit the BBC’s coverage of organisations considered illegal in Northern Ireland. The Prime Minister requested that the corporation did not carry live interviews with anyone associated with paramilitary groups. That avenue would be open to Gordon Brown but there has been no indication from Downing Street that it has been considered.

“Editorial decisions about who appears on Question Time are a matter for the BBC,” said a No10 spokesman.

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