Jacqui Smith, Britain's home secretary, said: "I'm delighted with the Lords' decision.
"My top priority is to protect public safety and ensure national security and I have signed Abu Qatada's deportation order which will be served on him today.
"I am keen to deport this dangerous individual as soon as I can."
But Tom Porteous, London director of Human Rights Watch, told Al Jazeera he found the decision "extremely disappointing".
He said the judgement "fundamentally undermines the global ban on torture".
"It sends a message not only to the British government but also to governments around the world that it's quite acceptable to send individuals to countries where they are at serious risk of torture on the basis of unenforceable and unreliable promises - diplomatic promises - that they will not be tortured," he said.
Amnesty International, the UK-based human rights organisation, also expressed concern over the ruling.
"It would be deeply worrying if the Law Lords' decision were taken by the UK government as a green light to push ahead with deporting people to countries where they will be at risk of abuses such as torture and unfair trials," Nicola Duckworth, a director at Amnesty, said.
Abu Qatada, whose real name is Omar Mahmoud Mohammed Othman, was described as Osama bin Laden's "right-hand man" by Baltasar Garzon, a leading Spanish judge.
He was granted refugee status in Britain in 1994.
The British government has said he has "long-established" links to al-Qaeda and armed groups in Algeria, Tunisia and Egypt.
Spain has accused Abu Qatada of being an associate of Abu Dahdah, who was implicated in the September 11, 2001 attacks on the United States, and videotapes of his sermons were found in the German apartment of Mohammed Atta, the presumed ringleader of the attacks.
The UK ruling could be appealed against in the European Court of Human Rights.