Charles Clarke, the Home Secretary, said evidence against Egyptian-born "C" no longer justified his indefinite detention in Woodhill high-security prison, Buckinghamshire, but declined to give any further reason for his release.
"C" was one of the first foreign suspects to be detained under emergency terror legislation hastily drawn up by ministers after the 11 September attacks. His release came less than 24 hours after another detainee, Abu Rideh, was granted bail by the Special Immigration Appeals Commission (SIAC) because his indefinite detention had worsened his psychiatric problems.
The remaining nine suspects held at Belmarsh and Broadmoor secure hospital are expected to be released on bail or unconditionally freed in the next few days. A tenth man, "G", was granted bail last year under conditions of house arrest.
In December, the Lords ruled that indefinite detention without trial was unlawful, prompting Mr Clarke to agree last week to replace Part 4 of the Anti-Terrorism Crime and Security Act 2001 with control orders that would allow ministers to place both foreign nationals and UK citizens accused of terrorism under house arrest.
He has faced a backlash from MPs, civil rights groups and the legal profession over the plans, which give the Home Secretary as much power over citizens as the Government exercised during the Second World War. Michael Howard, the Tory leader, is expected to join the criticism today by demanding alternatives to the proposed control orders.
Mr Clarke defended his plans in a private meeting with the Parliamentary Labour Party. He highlighted the threat by warning MPs evidence showed that attacks had been thwarted by anti-terrorism operations.
The Home Office said last night that the evidence against the detainees was under constant review and, as soon as they were no longer considered a threat, they were allowed to leave detention. Sources indicated that the activities of C's alleged associates had been disrupted, meaning he was no longer seen as a threat.
But Stephen Bowen, the Amnesty International UK campaigns director, said: "This man's release only underscores the arbitrariness and secretive nature of the draconian measures currently being used to detain people without charge in this country. What we need to see now is a scrapping of the Belmarsh system of detention as well as the envisaged control orders."
The director of the civil liberties group Liberty, Shami Chakrabarti, said: "This is a glimpse of the terrifying future where everyone may be subjected to detention on the basis of secret intelligence and a politician's whim."
C's solicitor, Natalia Garcia, said that the decision to release her client had come "completely out of the blue". He said: "In effect, the Home Secretary has now admitted C is no danger to anyone at all, which is what we've said from the very beginning, but it has taken three years and his life has been decimated in the meantime."
C was granted refugee status in the UK in 2001 after fleeing Syria. He told immigration officers he had been sentenced in Egypt to 15 years' jail for "alleged underground activities to topple the Egyptian regime". His brothers were also arrested and they confessed under torture and implicated C. The security services' first interview with C was on the day he received a letter from the Home Office stating that his claim for asylum had been successful.
The Government alleged that he supported Egyptian Islamic Jihad, which is a proscribed organisation under Part 2 of the Terrorism Act 2000, and which, it claims, had merged with al-Qa'ida. C denied any involvement in terrorist activities and during the SIAC hearing his lawyers alleged that the security services "were trying to build a case of reasonable suspicion having made no effort whatsoever to investigate the case".
Mr Clarke said to MPs: "Maintaining protection of national security and public safety is a top priority and I will continue to liaise closely with relevant authorities to ensure every practical step is taken to ensure a successful fight against terrorism while safeguarding individual liberties."
The Liberal Democrats said they planned to oppose the plans to keep terror suspects under house arrest. The party says such arrests would still need the UK to opt out of human rights treaties. They will unveil their own proposal today.Reuse content