The Government has run up a legal bill of more than £8 million trying to maintain its controversial control order regime, it was revealed today.
Details of the costs were released by the Home Office after it suffered a series of defeats in the courts by terror suspects who claimed the detention arrangements breached their human rights.
But Home Secretary Alan Johnson insisted the system remained an "important tool" to protect the public from terrorism.
And, in a separate report, the independent reviewer of terrorism legislation, Lord Carlile, said that abandoning the regime entirely would have a "damaging effect on national security".
Information about spending on control orders was disclosed by the department in a memo to the Commons Home Affairs Select Committee assessing their effectiveness.
It said the system had cost the Home Office some £10.8 million between April 2006 and August 2009. This included staff and administrative costs as well as legal expenses.
The memo went on: "The extensive internal and judicial scrutiny relating to control orders to ensure that they remain fair and justified, including the automatic review of all control orders by the High Court and the ongoing litigation on the control order regime, means that there are inevitably significant legal costs associated with the process (over £8 million of the £10.8 million total)."
The document admitted that was a "significant sum of money", and the Government was attempting to "minimise the costs".
"But viable alternatives to control orders, such as surveillance, would be considerably more expensive," it added.
"The reality is that without control orders there would be an unquantifiable increased risk to the public from controlled individuals."