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A radical Islamist cleric described by prosecutors as a key Al Qaeda operative in Europe cannot be deported from Britain to Jordan to face terrorism charges, judges ruled Monday in the latest twist in a protracted legal saga.

Britain's government has been attempting to expel radical preacher Abu Qatada since 2001, and immediately said it intended to mount an appeal against its latest setback at the country's courts.

Abu Qatada has previously been convicted in his absence in Jordan of terrorist offenses related to two alleged bomb plots in 1999 and 2000, and he will face a retrial if deported there from Britain.

Though the government insisted it had won assurances from Jordan over how Abu Qatada's case would be handled -- including from Jordan's King Abdullah II, who met with Cameron last week -- judges said there was a real risk that evidence obtained through torture would be used against the cleric.

In a ruling, Britain's Special Immigration Appeals Commission, which handles major terrorism and deportation cases, said it is not convinced that Jordan would guarantee Aby Qatada a fair trial.

It endorsed the January ruling of the European Court of Human Rights, which said that "not only is torture widespread in Jordan, so too is the use of torture evidence by its courts."

Britain's Home Office said it would challenge the decision at the Court of Appeal, and insisted it would oppose attempts by Abu Qatada's lawyers to have him released from prison on bail.

"The government strongly disagrees with this ruling," the ministry said. Home Secretary Theresa May was scheduled to address lawmakers on the issue later Monday.

Abu Qatada, a Palestinian-born Jordanian cleric whose real name is Omar Mahmoud Mohammed Othman, poses "an enormous risk to national security," government lawyer Robin Tam told Monday's hearing.

Prosecutors in British and Spanish courts have previously described Abu Qatada as a senior Al Qaeda figure in Europe who had close ties to the late Osama bin Laden.

British government lawyers have previously accused him of links with Zacarias Moussaoui, the only person charged in the United States over the Sept. 11, 2001, terrorist attacks, and with shoebomber Richard Reid. Audio recordings of some of the cleric's sermons were found in a flat in Hamburg, Germany, used by some of the Sept. 11 hijackers.

Authorities first attempted to deport him in 2001, and then detained him in 2002 under anti-terrorism laws which at the time allowed suspected terrorists to be jailed without charge. Though he was released in 2005 when the unpopular law was overturned, the cleric was kept under surveillance and arrested again within months to be held in custody pending his deportation to Jordan.