Britain's top court delivered a severe jolt to Prime Minister Tony Blair's post-September 11 security policies yesterday by ruling against the detention of nine foreign terrorism suspects without trial.

The British government, Washington's chief ally in its "war on terror", said it would send the controversial law under which the Muslim men are held back to parliament.

But it refused to release the nine - one of whom is accused of inspiring the September 11 US attacks - for security reasons.

The Law Lord judges ruled 8-1 in favour of the men whose imprisonment under draconian anti-terror laws, some for as long as three years, has become a cause celebre for rights activists who call their predicament "Britain's Guantanamo Bay".

"Indefinite imprisonment without charge or trial is anathema in any country which observes the rule of law," said one of the judges, Lord Donald Nicholls.

Among the inmates is Syrian cleric Abu Qatada, accused of being the spiritual inspiration for the lead September 11 attacker.

Qatada is also suspected of funding and inspiring top al Qaeda figures and other militants in the Middle East, North Africa, Afghanistan and Chechnya from his base in London.

The ruling was a setback for Mr Blair's government, which argues such severe measures are necessary for the wider good and opted out of the EU human rights' charter to enact them.

It came hours after Home Secretary David Blunkett, architect of UK anti-terrorism policies, resigned amid a scandal over allegations he abused his office to help a lover.

His successor Charles Clarke said the nine would stay behind bars while parliament looked at the law, which gives police powers to detain indefinitely, without trial, foreign nationals suspected of being involved in terror activities.

Crucially, it does not apply to British citizens.

"I will not be... releasing the detainees, whom I have reason to believe are a significant threat to our security," he said.

Lawyers for the nine, most of whom are in London's top security Belmarsh prison, demanded their immediate release.

"There is no escape route for the government whatsoever. It will provoke an enormous constitutional crisis if the government fails to act swiftly," lawyer Gareth Peirce said.

She said four of the detainees had gone mad due to their treatment, and attacked a suggestion the government may respond by widening the law to include UK as well as foreign suspects.

"Let them try to lock up British nationals indefinitely without trial. That would be a step no government here is prepared yet to take," she said outside court.

Rights campaigners were delighted by the judgement, saying they were ashamed of Britain's detention policy.

"It is a stain on the character of this country... It is our version of Guantanamo Bay," said Jeremy Corbyn, a left-wing legislator in Mr Blair's ruling Labour Party.

Massoud Shadjareh, head of Britain's Islamic Human Rights Commission, said: "It's the final nail in the coffin of this draconian piece of legislation under which the lives of 17 innocent people and their families have been mercilessly destroyed."

London argued detention without trial was the only way to deal with foreign suspects refusing to leave voluntarily but who cannot be deported under British law because they face death or mistreatment in their home countries.