LONDON - British judges on Monday upheld an appeal by terror suspect Abu Qatada against his extradition to Jordan, ruling that there was a risk of evidence obtained by torture being used against him.

The government in London immediately condemned the decision and said it would continue its fight to deport Abu Qatada, an Islamist preacher who has been described as Osama bin Laden's right-hand man in Europe.

The 51-year-old was convicted in his absence in Jordan in 1998 for involvement in terror attacks.

British interior minister Theresa May had ordered his extradition after she was given assurances by Jordanian authorities that no evidence gained through torture would be used against him in a retrial on his return to Jordan.

But the Special Immigration Appeals Commission, a semi-secret panel of British judges that deals with decisions on national security, said it could not be guaranteed that Qatada would receive fair treatment.

"We are satisfied that the Secretary of State should have exercised her discretion differently and should not have declined to revoke the deportation order," the commission said in its ruling.

"Accordingly, this appeal is allowed."

The European Court of Human Rights (ECHR) had ruled earlier this year that he could not be deported while there was a "real risk that evidence obtained by torture will be used against him".

The SIAC ruling said statements from Abu Qatada's former co-defendants -- Al-Hamasher and Abu Hawsher -- which were alleged to have been obtained by torture created a risk that his trial would be unfair.

It said last month while hearing his appeal that some of the evidence against him was "extremely thin".

May was due to address parliament later Monday.

The Home Office said it would seek leave to appeal.

"The Government strongly disagrees with this ruling," a Home Office spokesman said in a statement.

"We have obtained assurances not just in relation to the treatment of Qatada himself, but about the quality of the legal processes that would be followed throughout his trial.

"Indeed, today's ruling found that 'the Jordanian judiciary, like their executive counterparts, are determined to ensure that the appellant will receive, and be seen to receive, a fair retrial.'

"We will therefore seek leave to appeal today's decision."

Abu Qatada claimed asylum in Britain in 1993.

He has spent most of the last seven years in British jails and is being held in a high-security prison while he fights deportation.

In October Britain extradited another radical Islamist preacher, Abu Hamza, and four other terror suspects to the United States at the end of a long legal battle.