A London based think tank has revealed this week that an Islamist preacher currently imprisoned in the UK has been issuing pro-jihadist fatwas and anti-Semitic statements from inside a UK prison.

The Quilliam Foundation, a counter-extremism body set up in 2008 by former members of UK-based extremist Islamist organizations, has accused Abu Qatada, who they describe as "one of the world's most influential jihadi theologians", of inciting terrorism after they discovered that he has been issuing fatwas and statements from Long Lartin high security prison in Worcestershire, in the west midlands area of central England.

Jordanian national Abu Qatada has been in custody in the UK since August 2005, shortly after the July 2005 London bombing. Born in Bethlehem, the radical cleric entered the UK in 1993 using a forged United Arab Emirates passport and claimed asylum on ground of religious persecution. The following year he was granted asylum but in 2007 a British court ruled that he could be deported to Jordan where in 2000 he was sentenced in absentia to life imprisonment for his role in a plot to bomb tourists in Jordan for the millennium celebrations.

Richard Reid, the mid-Atlantic shoe bomber, and Zacarias Moussaoui, both jailed for involvement in terrorism, are said to have sought religious advice from him. Nineteen audio cassettes of Abu Qatada's sermons were found in the apartment of Mohamed Atta when it was searched after the 9-11 attacks. According to the indictment of the Madrid al-Qaeda cell, he was also the spiritual leader of al-Qaeda in Europe.

Research done by the think tank has shown that three major statements have circulated globally on English and Arabic-language jihadist websites, the most recent being only last month.

One statement praises "the mujahideen" of al-Qaeda and the "martyrs of Hamas" while cursing "the Jews" and "Crusaders".

According to Quilliam, Abu Qatada said in January, during Operation Cast Lead: "I congratulate the mujahideen and the people of Gaza, and may Allah have mercy on the martyrs and make us follow them, and may Allah curse the Jews and the rulers of apostasy and the crusaders - amen, amen."

In another statement, made in June 2008, he justified jihadist attacks on Muslims who join armies and police forces in non-Muslim countries and Muslim countries that oppose al-Qaeda.

"Whoever fights for taghoot is kafir and fighting and aiding with your hand and weapons is the highest form of allegiance, as Allah says "who gives allegiance to them, he is from them"…What then would be the state of those who fights to aid and strengthen them? There is no doubt that he is a kafir and apostate, and his apostasy would be doubled if he fights under their banner against the people of Islam like those who fight the Muslims in Palestine, Iraq, Afghanistan, Chechnya or Somalia. This is a ruling that has the consensus of the scholars that no Muslim can disagree with once he knows the ruling," he said.

Last month he attacked the UK government accusing it of opposing Islam.

"We have defeated the British government, by the virtue of Allah, the most high, and in our imprisonment, there was an uncovering of their filthiness and their criminality and their false claims of humanism. And we were able to demonstrate to the Muslims in Britain specifically, that the government is one which opposes Islam and the Muslims. And a fracture, which can never be set after that, took place by the virtue of Allah.

"May Allah give the Mujahideen and their leaders the best reward, and may Allâh give the callers to the truth the best reward, because had it not been for them, the disbelievers would have entered our women's quarters and we would have become nothing but dogs that lick up their crumbs," he added.

"Abu Qatada is one of the worlds most influential and dangerous jihadist clerics," said James Brandon, a senior researcher at Quilliam and author of a forthcoming report'Al-Qaeda in our Prisons'. "His fatwas justifying terrorist violence have directly led to jihadist attacks in Algeria and Iraq, as well as helping to inspire the 9-11 attacks and the 2003 Madrid bombings.

"It is terrifying that the Prison Service has allowed Abu Qatada to repeatedly distribute pro-jihadist texts from within British prisons. The very reason that he has been detained is because he is a threat to public safety by inciting terrorism and violence."

"We have seen the bloody outcome of terrorist incitement against Jews and others," said Mark Gardner, director of communication at the Community Security Trust, a charity that represents British Jewry to police, government and media on anti-Semitism and security issues. "These claims concerning Abu Qatada must therefore be dealt with as a matter of the utmost importance."