Abu Qatada has won an appeal against deportation to Jordan where he was to face trial on terror charges, according to a ruling by the Special Immigration Appeals Court.
The decision was made despite Theresa May receiving special assurances from Jordan that evidence gained using torture would not be used against him.
The judge's provisional view is that the radical cleric could be granted bail with a 16 hour curfew.
The Home Office said it "deeply disagrees" with the ruling and will seek leave to appeal.
A Home Office spokesman said: "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."
Siac found that Qatada's right to a fair trial would be breached because evidence obtained via torture could be used during his re-trial in Jordan.
Qatada had claimed that there was a risk that he himself would be tortured or badly treated in Jordan, however this was rejected.
His legal team also maintained that even if he was acquitted at re-trial, he could be kept in prison under Jordanian law if the authorities decided he was "a danger to the people", therefore breaching his right to liberty.
This was also rejected.
May is due to make a statement to the Commons on the ruling this afternoon.
Home Secretary Theresa May
LONDON, ENGLAND - APRIL 19: Home Secretary Theresa May leaves the Houses of Parliament after making a statement defending the Home Office's handling of the Abu Qatada affair and possible error on dates on April 19, 2012 in London, England. Extreme Muslim Clerir Abu Qatada's deportation to Jordan is on hold after his lawyers filed an appeal to the European Court of Human Rights. (Photo by Matthew Lloyd/Getty Images)
Radical Islamist cleric Abu Qatada
Radical Islamist cleric Abu Qatada sits in a car as he leaves a Special Immigration Appeals Hearing at the High Court in London to go to jail after being re-arrested on April 17, 2012. British authorities re-arrested Abu Qatada today and began a fresh bid to deport him, saying they had resolved concerns about his treatment in Jordan. Abu Qatada was found guilty in his absence in 1998, but Jordan has promised to quash the conviction and give him a new hearing before civilian judges, with independent defence lawyers and the right to question witnesses, she said. AFP PHOTO / MIGUEL MEDINA (Photo credit should read MIGUEL MEDINA/AFP/Getty Images)
FILE - An undated 2005 image made by the British Prison Service showing Abu Qatada making a televised appeal from Belmarsh high security prison, in London calling for the release of hostage British Norman Kember in Iraq. The extremist cleric described as among Europe's leading al-Qaida operatives should not be deported to Jordan to face trial because of the risk evidence obtained through torture would be used against him, Europe's highest court ruled Tuesday, Jan. 17, 2012. After a 6-year legal battle, the European Court of Human Rights ruled that deporting Abu Qatada from Britain _ where he is in prison custody _ would "give rise to a flagrant denial of justice." (AP Photo/ H.M. Prison Service, File)
Theresa May, Mohammad Raoud
In this photo provided by Jordanian News Agency PETRA, Jordanian Interior Minister Mohammad Raoud, left, greets British Home Secretary Theresa May, right, upon her arrival to discuss the deportation of Muslim cleric Abu Qatada, in Amman, Jordan, Monday, March 5, 2012. British Home Secretary Theresa May said Monday that talks in Jordan had not produced a deal aimed at overcoming a European ban on deporting a radical Islamist cleric to the Arab country. (AP Photo/PETRA)