The Government's anti-terrorism laws suffered a major setback yesterday when a High Court judge quashed control orders on six suspected Iraqi terrorists who had been under house arrest for 18 hours a day.

John Reid, the Home Secretary, insisted that control orders were necessary to protect the public

Mr Justice Sullivan ruled that restrictions imposed on the men's liberty by the Home Office were so severe that they breached article 5 of the European convention on human rights, which prohibits detention without trial.

The ruling left the Government's control order regime in tatters and threatened a fresh confrontation between ministers and the judiciary over the interpretation of the convention.

The orders were made under the Prevention of Terrorism Act 2005, which Charles Clarke, the former home secretary, pushed through Parliament in only 19 days after powers detaining terrorist suspects without trial in Belmarsh Prison were declared unlawful.

John Reid, the Home Secretary, said the Government would seek to overturn the decision in the Court of Appeal. The appeal hearings are expected next Monday. Until then, the six will remain subject to the restrictions.

Mr Reid insisted that control orders were necessary to protect the public from a threat from foreign nationals who could not be deported.

"Public safety is our top priority," he said.

Mr Justice Sullivan ruled that the Home Secretary had no power to make the orders, which breached article 5 of the convention, so they must be quashed.

He said the six men, all single, were asylum seekers who had been arrested under the Terrorism Act then released without charge.

Under the orders, one was allowed to live at home but the others were required to live at designated addresses away from their home areas.

They were obliged to remain indoors between 4pm and 10am and even outside those hours were subject to severe restrictions. Their access to telephones and the internet was strictly curtailed.
 
They were required to live alone in one-bedroom flats and relied on friends and acquaintances for social contact. Visitors had to provide, in advance, their name, address, date of birth and photographic identity.

The authorities could search the men's homes at any time of the day or night - "rather like a prisoner in his cell", the judge said.

Such restrictions on their ability to live a normal life were "the antithesis of liberty and equivalent to imprisonment", he said.

When allowed out, they could not meet any person without prior arrangement and could not attend meetings. Mr Justice Sullivan said: "I am left in no doubt whatever that the cumulative effect of the restrictions has been to deprive them of their liberty in breach of article 5."

The collective impact of the controls could not be described as mere restrictions on movement.

In an open prison, a prisoner would at least be able to associate with other inmates and, if his request for a particular visitor was refused, he would be able to use a well-established complaints procedure. No appeal mechanism was available to those under control orders.

"Their lives are not free but are for all practical purposes under the control of the Home Office," the judge said.

It was not the first time that Mr Justice Sullivan had clashed with the Government over anti-terrorism laws.

Last month he ruled that nine Afghan hijackers should be allowed to stay in Britain, blocking Home Office moves to deport them. Tony Blair described that ruling as an "abuse of common sense".

The latest ruling is a serious embarrassment for the Prime Minister just over a week before the first anniversary of the July 7 London bombings.

It also presents Mr Reid with a full-blown crisis less than two months after being appointed to take charge of the deeply demoralised and "dysfunctional" Home Office.

It will put fresh pressure on the Government to consider renouncing parts of the human rights convention, which judges have repeatedly used to block moves to detain or deport terrorist suspects believed to pose a threat to national safety.

Downing Street confirmed last night that the Government was reviewing the way the courts interpreted the Human Rights Act, which incorporates the European convention into British law.

MPs approved the control orders after the Belmarsh ruling in December 2004, when the law lords ruled that detention of suspected foreign terrorists without trial was disproportionate and discriminatory.

As well as giving limited powers to ministers, the 2005 Act allows a court to impose a control order depriving a terrorist suspect of his liberty.

First, however, the Government must derogate from - opt out of - article 5.

Before opting out, the Home Secretary must be satisfied that there is a "state of emergency threatening the life of the nation" and that the measures he is proposing are "strictly required by the exigencies of the situation".

Before the London Tube and bus bombings, Mr Clarke told MPs that he had been advised by the police that deprivation of liberty, although valuable, was not "strictly required".

Unless Mr Reid overturns yesterday's ruling on appeal, he will either have to reduce the severity of the restrictions on the men - and any others in a similar position - or derogate from the convention.

The independent reviewer of terrorism legislation, Lord Carlile of Berriew, said the Government should amend the control orders to make them comply with article 5 of the convention.

He believed it would be possible to reduce the scope of curfews and lift some restrictions on visitors. It would be "unacceptable" for the Government to derogate from article 5.

David Davis, the shadow home secretary, said that ministers had failed to "think through" the implications of the control orders after their earlier defeat.

Shami Chakrabarti, the director of Liberty, said control orders substituted long-term punishment based on secret intelligence for charges, evidence and proof.