France's favourite stand-up comedian has been forced to apologise for claiming that the 9/11 terrorist attacks on the US seven years ago tomorrow were an "enormous lie" orchestrated by the American government.

The allegations by Jean-Marie Bigard have caused consternation in France because the comedian - who specialises in foul-mouthed, scatological and sexist humour - is a close friend of President Nicolas Sarkozy.

On a radio show last Friday, the comedian interrupted a discussion on American politics, to say that it was "absolutely sure and certain" that the US government had stage-managed the 9/1l attacks in which 2, 896 people died.

"The two planes which crashed in a forest and on the Pentagon never existed. There never were any planes. It's an absolutely enormous lie," M. Bigard said.

"It was an American missile which hit the Pentagon. That's now been proved. It was a programmed demolition."

Asked by the presenter of the show on Europe 1 radio where he found his information, M. Bigard replied "the internet".

In a statement to Agence France-Presse yesterday, M. Bigard said that he wanted to "apologise to everyone".

"I will never speak again about the events of 11 September," he said. "I will never express any more doubts."

He stopped short, however, of saying that he accepted that his comments were untrue.

The comedian's remarks are said to have caused embarrassment at the Elysee Palace. President Nicolas Sarkozy has gone out of his way to present himself as an Americophile politician and to distance himself from the gut anti-Americanism of a minority of the French Left and Right.

M. Bigard, unknown abroad but capable of filling large concert halls in France, is part of M. Sarkozy's large coterie of show-business friends. There was astonishment last December when the comedian - a kind of French Bernard Manning but a devout Catholic - accompanied M. Sarkozy on an official visit to Pope Benedict in Rome.

Conspiracy theories about 9/1l remain popular among a fringe of French people. They were first publicised in 2002 by a French author, Thierry Meyssan, in a book which was widely rubbished by the mainstream French press.

Comments by the actress Marion Cotillard, giving credence to the conspiracy theories, caused fury in the United States in January. The comments, made by Mme Cotillard several years ago, were unearthed after she won an Oscar for the Edith Piaf bio-pic, "Vie en Rose".

A Canadian conspiracy movie about 9/11, "Loose Change", has attracted more than 100,000 viewers on the French internet video site "Dailymotion" in recent weeks. The highly selective evidence presented in the movie appears to have been the basis of the remarks by M. Bigard.