Prime Minister David Cameron, and predecessors Gordon Brown and Tony Blair, repeatedly stated their intention to ban Hizb ut-Tahrir, but such action has not yet been taken.
Mr Wahid's appearance last week was the first of a number of appearances by extremist speakers. Norman Finkelstein, the controversial American-Jewish anti-Israel academic, was in five campuses this week on a speaking tour.
In Exeter, Israeli-born antisemite Gilad Atzmon spoke to a pro-Palestinian society after the university's Student Guild rejected calls to ban him from the campus.
BNP leader Nick Griffin has been invited to speak at Nottingham University's debating society on November 24. He is due to take part in a discussion on the death penalty.
Last Thursday Deputy Prime Minister Nick Clegg made an unexpectedly strong attack on the Federation of Student Islamic Societies (Fosis) and its "failure to challenge sufficiently terrorist and extremist ideologies" during a speech to the Community Security Trust in Manchester.
Mr Clegg said there needed to be a "tough and smart approach" to tackling general bigotry and campus hate. He said: "Some organisations we have no choice but to shut down. If we are concerned enough about their activities we will, as a last resort, consider proscribing them. We won't provide funding for groups who advocate intolerance." He said the government should "absolutely not" treat Fosis as "a credible partner."
Hizb ut-Tahrir's Abdul Wahid spoke at the annual Al Quds Day march in Trafalgar Square in August, where he spoke of his "respect" for "those brothers who are resistance fighters, making jihad, making life tough for the Israelis and the Zionists" and called on neighbouring states to "release their armies to liberate that land".
Rupon Haque, who helped organise and promote the SOAS event on behalf of the student union's Belief and Reason Society, is a Hizb ut-Tahrir supporter and has regularly promoted it on social networking sites.
Also on the panel at SOAS was Ahmed Shebani, founder of Libya's Democratic Party. When he told the audience of the need for Libya to normalise relations with Israel he
was reportedly shouted down and called a "kaffir".
Anti-extremist groups Stand for Peace and the Institute for Middle Eastern Democracy have been aware of the Belief and Reason Society's activities for some time.
Stand for Peace director Hasan Afzal said: "Including a Hizb ut-Tahrir speaker in what looks to be an ordinary student debate with a respected opponent and seemingly normal topic, legitimises Hizb ut-Tahrir."
Sam Westrop, IMED director, said: "It is imperative that students, both Jewish and Muslim, keep an eye on the sort of ideas being espoused by student organisations. The concepts of interfaith and debating groups are frequently manipulated and employed to sanitise radical organisations' virulent ideas."
Norman Finkelstein's speaking tour, organised by the Palestinian Return Centre, included campuses in Leeds, Manchester, Nottingham and Birmingham. He was due to speak at the University of London's Logan Hall tonight.
The author of The Holocaust Industry faced a large demonstration organised by the Union of Jewish Students and Leeds JSoc at his first talk on Monday. Bruce Rothberg of Leeds JSoc said: "It beggars belief that our Palestine Solidarity Group would invite someone who has compared Israelis to Nazis, proclaimed his support for Hizbollah's attacks on civilians, and questioned the credentials of Holocaust survivors."
On Tuesday evening, students from Exeter JSoc protested as their university Friends of Palestine Society hosted Israeli-born antisemite Gilad Atzmon.
Despite complaints from Jewish students, the Student Guild refused to cancel the event. Atzmon's latest book, The Wandering Who?, questions elements of the Holocaust and includes one chapter entitled Swindler's List.
He told the audience of 30 that "Hitler was right" and "antisemitism doesn't exist". The
university's Student Guild had assured UJS it would stop the event if Atzmon made antisemitic remarks but failed to take any action. A number of Jewish students walked out in disgust. The Guild's chief executive, James Hutchinson, insisted that Atzmon's remarks were made during a complex discussion in which Atzmon said that in the event of a nuclear war started by Israel, "some Europeans might say that Hitler was right".
Mr Hutchinson added that the remark about antisemitism was made by Mr Aztmon in reference to his belief that antisemitism did not exist within the pro-Palestinian movement debating the Israel-Palestinian conflict.
Nick Davis, president of the Guild, said: "We ensured a large staff and security presence at Gilad Atzmon's talk to ensure a quick and effective shutdown in the event that our equal opportunities policy was breached. Gilad Atzmon's speech was clearly provocative, but when his comments were contextualised they did not breach our policy. We are working closely with the Jewish Society to discuss their concerns."
Exeter JSoc president Ben Salamon said: "We hope our protest will help prevent future events like this from being permitted at Exeter University."
Mr Willetts declined to comment on this week's events.
Additional reporting by Jonathan Kalmus
