The BBC was unable to broadcast a programme in which a Gaza flotilla participant was forced to defend himself against allegations of Holocaust denial because of transmission problems.
Ismail Patel, chairman of the Leicester-based Friends of Al Aqsa group, appeared on Sunday's episode of The Big Questions to discuss the topic "Is Israel acting immorally?".
Among those defending Israel were Jonathan Hoffman of the Zionist Federation, Rabbi Yitzchak Schochet and Shoah survivor Martin Stern.
The trio alleged that Mr Patel's group website links to Holocaust denial material. They also claimed he had previously said the September 11 terrorist attacks were caused not by Islamic fundamentalists, but by the CIA and Mossad.
Mr Patel denies all the allegations against him.
But viewers were unable to see their discussion after a satellite failed and the live show, presented from Leicester by Nicky Campbell, went off the air.
The BBC said it was also unable to upload the programme to its iPlayer service because of the "technical difficulties" which rendered the programme "incomplete".
Mr Patel had been on the Mavi Marmara boat when Israeli commandos boarded it and clashed with activists. Nine of his shipmates died.
Friends of Al Aqsa describes itself as a "non-profit making NGO concerned with defending the human rights of Palestinians and protecting the sacred al-Aqsa Sanctuary in Jerusalem".
Mr Hoffman said: "On the website there are links to Holocaust denial material. This was pointed out by Rabbi Schochet on the show.
"Martin Stern has been to lectures Mr Patel has given to students where he has said Islamic fundamentalists did not cause 9/11 and blamed the CIA and Mossad.
"When Nicky Campbell asked about the 9/11 issue Mr Patel denied it. But Martin said 'I'm sorry, but I was there and you said it'. That blew the credibility of his flotilla testimony."
Mr Hoffman criticised the BBC's failure to provide the show online: "At a time when the people who were on the boats are speaking in public, here is an example of someone whose testimony is completely unreliable and no one will see the programme. It has to be put in the public domain."
Rabbi Schochet said: "Collectively we put up a strong case for Israel and completely discredited Mr Patel in front of the studio audience. It was a shame it couldn't be in front of a wider television audience."
Speaking after the show, Mr Patel said: "It's regrettable that the people who tried to defend Israel went on a personal attack against me because none of them had any evidence. The idea that I deny the Holocaust is ridiculous and preposterous. It was one of the worst tragedies of the last century.
"They said I promote antisemitism on the website. There is no proof. I was very sad that they degraded the debate to that level. I have Jewish friends right across the spectrum from strictly Orthodox to Progressive communities.
"I have written about 9/11 in the media. It was carried out by Bin Laden, who can deny that?"
He said the Jewish panellists had attempted to divert attention from Israel and "trivialised the tragedy of the Jewish people".
The failed broadcast sparked conspiracy theories on the show's online message board. After the programme went off air one commenter wrote: "Coincidence? I very much doubt it. Is Israel acting immorally? Asking this is and has been taboo. Someone intends that it remain so."
Another post added: "I believe there were no 'technical' problems... rather a block on discussion of a very popular and emotional subject: Israel's disregard for international law and treatment of the Palestinians."