A cornerstone of the Government's security policy was thrown into doubt today after a High Court judge ruled the use of control orders on terrorist suspects to be unlawful.

In a ruling that instantly re-ignited the feud between the Government and the judiciary, Mr Justice Jeremy Sullivan said that powers enshrined by the orders were so severe that they amounted to a deprivation of liberty without a trial and, as such, breached European human rights legislation.

Quashing orders against six men - one British citizen and five Iraqis referred to only by initials - he told the High Court in London: "The [Home Secretary] had no power to make the orders and they must therefore all be quashed."

Control orders were introduced in April last year after the courts rejected post-September 11 emergency powers allowing police to imprison suspected foreign terrorists indefinitely without trial.

The measures - which give the Home Office the power to severely restrict the lifestyles of terror suspects, including placing them under conditions akin to house arrest - were steered onto the statute book days before the last general election. It is believed that 14 control orders have since been imposed.

The orders - which also allow the use of electronic tagging, the conviscation of passports and a ban on associating with other named suspects - can remain in force for up to 12 months before being reviewed by the Home Secretary.

The powers were drafted to circumvent European Convention rules which state that a country may not deprive someone of their liberty without a trial unless it first declares an emergency and "derogates" - or departs from - the preservation of basic human rights.

The Home Office has argued that control orders do not constitute "deprivation of liberty" and it therefore is not necessary to declare that Britain is in a state of emergency. Even after the London bombings of July 7 last year, lawyers have warned that such a claim could be difficult to substantiate.

Mr Justice Sullivan disagreed, ruling that the men had indeed been deprived of their liberty without trial.

His ruling will enrage MPs, and reactivate the row between the Government and the judiciary over the balance between public safety and human rights.

Tony Blair, the Prime Minister, has repeatedly criticised judges for placing too much emphasis on the rights of suspects, and stated earlier this month that the legal system needed to be "rebalanced" in favour of protecting the public.

John Reid, the Home Secretary, said that he would seek to overturn the decision in the Court of Appeal.

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