Britain asked Jordan to pardon radical Islamist preacher Abu Qatada because evidence used to convict him of terrorism there was obtained through torture, a British diplomat told a court hearing on Thursday.

Britain is seeking to extradite the 51-year-old cleric, who has been accused of ties to al-Qaida, and has sought guarantees that he will not be mistreated in Jordan. Abu Qatada is appealing an extradition order before a special immigration tribunal.

The Palestinian-born Jordanian cleric, whose real name is Omar Mahmoud Mohammed Othman, has been convicted in absentia in Jordan over bomb plots and faces retrial if extradited.

Britain has signed an agreement with Jordan which it says ensures the preacher will not face ill-treatment, but Abu Qatada's lawyers say the deal does not offer sufficient protection.

Anthony Layden, a former British ambassador to Libya and a specialist in negotiating diplomatic guarantees, told the tribunal that British officials had sought a pardon during negotiations over Abu Qatada's fate.

He said the issue was raised at a meeting in Jordan in February involving that country's officials and a British government minister, James Brokenshire.

"I think the question of a pardon had been asked earlier and Mr. Brokenshire was asking for an answer," said Layden, who is appearing as an expert witness in the case.

He said Jordanian officials declined to pardon Abu Qatada and also refused to promise that they would not rely on statements obtained through torture during any prosecution.

Abu Qatada, who has been described in British and Spanish courts as a senior al-Qaida figure in Europe, has fought attempts to extradite him from Britain since 2001.

Earlier this year, he was denied permission to take his case to a European court, but he is appealing to the Special Immigration Appeals Commission, a semi-secret court that handles deportation and national security cases.