BRITAIN has resorted to detaining as an illegal immigrant a man regarded as one of al-Qaeda’s most dangerous terrorists.

Abu Doha, whose various aliases include “The Doctor”, has been in Belmarsh highsecurity jail for almost six years facing extradition to the United States on charges of running a jihad training camp in Afghanistan and plotting to blow up Los Angeles airport.

But the US has been forced to drop the case against him after an informer refused to give evidence.

A British judge described the extremist network created by Abu Doha as “one of the most significant groups of terrorists in the United Kingdom and a continuing significant threat to its security”.

But Abu Doha currently faces no terrorist charges here and Britain has had to use immigration powers to keep him in prison as it seeks to deport him to his native Algeria.

His lawyers are fighting that move and are expected to claim, when the case goes before the secretive Special Immigration Appeals Commission (SIAC) in January, that he would be tortured if returned to Algiers.

If the commission refuses to deport Abu Doha, the Home Secretary would have to resort to seeking his continued detention or agree to strict bail conditions under the discredited system of control orders.

Amnesty International said that it was concerned that the attempt to deport Abu Doha to Algeria, where allegedly he is associated with the GSPC terror group, was akin to “extradition in disguise” to a country with a reputation for torturing suspects.

An Amnesty spokesman said: “The Government says Abu Doha is a serious threat to national security. The nagging question is why it has not proceeded against him here in Britain. If he is suspected of committing offences, then there is an obligation to bring him to trial.”

Abu Doha, whose real name remains a mystery, was arrested in February 2001 as part of Operation Odin, a major anti-terrorist swoop aimed at preventing a series of planned suicide bombings in Germany and France.

The Algerian — a familiar figure at Finsbury Park mosque where Abu Hamza al-Masri, the radical cleric, preached — was carrying a false passport and attempting to board a flight to Saudi Arabia when detained.

A search of a council flat he used in Islington, North London, uncovered a haul of terrorist paraphernalia including a silver handgun, a telescopic rifle sight, dozens of false identity documents, 100 black berets and extremist videos.

He was charged with conspiracy to defraud but the case was discontinued. A number of European countries expressed interest in questioning him, and the US presented a strong case for his extradition.

The Americans already had in custody Ahmed Ressam, one of Abu Doha’s lieutenants, who was arrested in December 1999 en route to attack Los Angeles airport with explosives in the boot of his car.

He co-operated with the US authorities for a number of years, giving invaluable information about al-Qaeda camps in Afghanistan and Abu Doha’s network of North African extremists across Europe and North America.

But in August last year, he withdrew co-operation and the case against Abu Doha foundered. He has subsequently been sentenced to 22 years in jail.

Abu Doha’s case has also highlighted major difficulties in the SIAC system. This year, lawyers discovered that material presented by the intelligence services in his case contradicted evidence given in another appeal. The discrepancy led to severe criticism of the Home Office by SIAC judges.

The scandal has provoked further calls for the abolition of the system, which prevents detainees and their legal representatives from seeing the intelligence material that leads to their imprisonment.

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