Britain's interior ministry said on Monday that it had applied for permission to appeal against a decision by judges preventing terror suspect Abu Qatada from being extradited to Jordan.
"We confirm that we have submitted our grounds for appeal," a Home Office spokesman told AFP.
A judge will now consider the ministry's application for an appeal, which can be made only on a point of law.
Abu Qatada -- dubbed Osama bin Laden's right-hand man in Europe -- was released last month following the ruling that he could not be extradited over fears that evidence obtained through torture could be used in his trial.
The radical Islamist cleric's release was a severe blow to the British government, which has kept him in custody for most of the last decade and repeatedly tried to send him to Jordan to face trial.
Abu Qatada was convicted in absentia in Jordan in 1998 for involvement in terror attacks, but British and European judges have accepted his argument that evidence obtained by torture might be used against him in a retrial.
Prime Minister David Cameron said last month that he was "completely fed up with the fact that this man is still at large in our country".
Abu Qatada, a Jordanian of Palestinian origin in his early 50s, is currently under curfew 16 hours a day and is wearing an electronic tag, but he is free to leave his home in northwest London between 8:00 am and 4:00 pm.
The European Court of Human Rights 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" in a possible retrial.
Home Secretary Theresa May ordered his extradition anyway after Jordan gave assurances that he would be treated fairly.
But last month, the Special Immigration Appeals Commission -- a semi-secret panel of British judges that deals with national security matters -- agreed with the European judges that he should not be deported, and he was freed on bail.
The cleric, whose real name is Omar Mohammed Othman, arrived in Britain in 1993 claiming asylum and has been a thorn in the side of successive British governments.
Videos of his sermons were found in the Hamburg flat used by some of the hijackers involved in the September 11, 2001 attacks. He has also defended the killing of Jews and attacks on Americans.
A Spanish judge once branded him the right-hand man of late Al-Qaeda leader Osama bin Laden in Europe, although Abu Qatada denies ever having met bin Laden.