Control orders were always considered the third-best option for dealing with terrorist suspects against whom prosecutions could not be mounted in the courts.

They arose in response to the Human Rights Act making it impossible to deport a foreign national to a country where they might face torture or death. The orders under which terrorist suspects are subject to a range of restrictions – stopping short of house arrest – were forced upon ministers when the law lords ruled that holding terrorist suspects in jail indefinitely was unlawful.

Ministers insist that prosecution is their first option but admit that much of the “evidence” against the suspects would not be sufficient to bring a prosecution. Their second option was detaining suspects in prison, but when the law lords ruled that this was unlawful, Charles Clarke, then Home Secretary, brought in the control order regime.

It has involved secret court hearings with specially selected lawyers being informed of the evidence against suspects. However, the suspects themselves are not told the full details of the alleged evidence gathered against them.

The control order involves the Home Secretary certifying that a suspect is a threat to the country on the basis of evidence placed before him by the intelligence services. Once certified, a control order is put in place under which the suspect is placed under a curfew together with a range of restrictions such as no access to mobile phones or the internet and curbs on whom they can meet and where they go.

However, the system has been beset by problems with the courts ruling that curfew of 18 hours amounts to a form of house arrest. This forced ministers to introduce what has become known as “control order lite” with curfews limited to between 12 and 14 hours.

Last night’s disclosure that a further three controlees have absconded is another blow to the control order regime and will add to pressure on the Government to find an alternative.

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