The Big Question: What are control orders, and are they effective against terrorism?

Why are we asking this question now?

Three men have gone on the run after breaching the terms of their control orders, which are supposed to ensure that terrorist suspects do not fall off the authorities' radar.

Brothers Lamine and Ibrahim Adam did not contact the private company monitoring them on Monday, and Cerie Bullivant failed to report at his local police station the following day. The three men clearly planned to vanish together and officers are working on the theory that they will try to flee the country to join Islamist extremists.

Six of the 22 people put on control orders since they came into force two years ago have absconded, leaving a major question-mark over the survival of the controversial scheme. It has been dogged by criticism from opposition parties and civil liberties groups for being authoritarian and denying the basic right to freedom. The number of suspects going missing makes it hard even to argue that they are an effective tool against the terrorist threat.

Why were control orders introduced?

The scale of the threat to Britain changed fundamentally with the September 11 attacks on the United States in 2001 and the Government has brought in a succession of counter-terrorist measures in response. Ministers faced a particular problem with foreign nationals suspected of involvement in terrorism, but against whom there was not enough evidence to bring a prosecution. Initially they were locked up but their detention was ruled illegal in the courts, forcing ministers to cast around for alternative sanctions.

Returning foreign terror suspects to their home countries was not possible in many cases as they mainly came from north African nations with a history of torture and deporting them fell foul of the European Convention on Human Rights. Ministers turned to the concept of control orders, amounting to a loose form of house arrest, as the next best option. After a lengthy parliamentary battle, control orders became law in the 2005 Prevention of Terrorism Act.

What restrictions can be imposed and who has been targeted?

Control orders, which are imposed by John Reid, the Home Secretary, and have to be approved by immigration courts, subject terror suspects to strict restrictions on their activities. Their use has been expanded to cover Britons as well as foreigners, and eight of the 17 orders currently in force are on UK nationals. Those considered to represent the most serious risk to national security can be ordered to observe a curfew (the maximum length of which is being fought over in court) and to live at one address. They can be electronically tagged, face restrictions on who visits them, be banned from accessing the internet, and only allowed to worship in a particular mosque. At the "lower end", which included the three men who absconded this week, suspects can be ordered to surrender their passports and report daily to a monitoring company or to police.

What do the critics of the system say?

Civil liberties groups and Muslim organisations argue that control orders fly in the face of natural justice because suspects can effectively be deprived of their freedom on the basis of secret information and without even being accused of a crime.

They argue that potentially dangerous people should be brought to court and say that more convictions could be achieved if the Government removed the ban on intercept evidence being allowed in terrorist prosecutions.

The accusation that the orders are a disproportionate response to the perceived terrorist threat has been held up in court. Last year a British citizen, known only as M B, won a High Court declaration that the restrictions on him were "incompatible" with human rights laws and had been imposed without a fair hearing.

Since then the Government has suffered a stream of court defeats on the policy, although the Home Secretary scored a legal victory last week when judges allowed his appeal against a court ruling which had forced him to water down a control order. The issue is likely to be fought over all the way to the House of Lords. Critics have said some of the blame for the legal uncertainly must lie at the Government's door as parts of the 2005 Act were couched in vague terms.

What is the Government's defence?

Tony Blair mounted a less than vigorous defence of the system as he summed up the justification for control orders. He described them as "very much a second best option", admitting: "They are not a strong method of keeping people under control. They are the best we can do however within the legislation that exists." Mr Reid is frustrated at having to rely on control orders, protesting that he is having to act with one hand tied behind his back and has said the system is not tough enough to be truly effective. However, the Government points to other action being taken against terrorism, including doubling the period of time that suspects can be questioned without charge to 28 days and to new offences of glorifying and inciting terrorism.

It also insists that terrorists are brought to court wherever possible, pointing to the recent convictions of five men for planning to murder hundreds of people in the fertiliser bomb plot.

What could replace control orders?

Mr Reid made clear yesterday that if the Government loses its court battle over control orders it is prepared to take the drastic step of opting out of parts of the European Convention on Human Rights to allow it to impose tougher restrictions on suspects. That would be a politically unpalatable step for many Labour MPs, although the Home Office suspects it would have widespread public support.

Mr Reid's preferred option would be to persuade other European countries to overhaul the convention to reflect the nature of the terrorist threat and last week raised the subject with other European interior ministers. Practically speaking, however, any "modernisation" of the convention could take years to accomplish.

Before 27 June, when he steps down along with Mr Blair, he is planning to set out a fresh raft of proposals for combating terror. Whoever succeeds Mr Reid as Home Secretary will discover that tightening security has become the main item on the agenda.

Control orders in numbers

Introduced: March 2005

Number imposed: 22

Number imposed and then not renewed: 5

Number currently in force: 17

Number in force against UK nationals: 8

Number in force against foreign nationals: 9

Number of people who have absconded from control orders: 6

Number of absconded people found: 0

So should control orders be scrapped?

Yes...

* Control orders have fallen into disrepute with the disappearance of six suspects

* Imposing fundamental restrictions on liberty and movement without trial is an affront to human rights

* More suspects could be brought to court if the use of telephone tap material was allowed

No...

* They are the strongest option open to the authorities who are barred from detaining suspects or deporting some foreign nationals

* Despite their weaknesses, they keep tabs on people whose free movement around Britain could threaten national security

* Their very existence sends a powerful deterrent message to people who might otherwise be caught up in terrorist activity