Prime Minister Gordon Brown has announced he wants to extend the time police are allowed to hold a terrorist suspect before they are charged or released.
He has put four options to MPs for debate before a decision. So what are the options?
THE CURRENT SYSTEM
Since July 2006 the police have been allowed to hold a terrorism suspect for up to 28 days without charge. Detention is subject to strict legal controls:
The Crown Prosecution Service is responsible for considering and making applications to extend detention beyond 14 days. Each application is made with the lead investigator present and defence solicitors are given a written document on the grounds for extended detention. The senior police officer can be questioned by the defence during the hearing.
OPTION ONE: EXTEND TIME LIMIT AND SAFEGUARDS
The government's preferred option is to extend the time limit but also introduce more judicial and parliamentary oversight.
Under this system additional oversight would be triggered by an application to go beyond 28 days detention. Any application for each additional seven days (beyond the first 28 days) would need to be approved by the Director of Public Prosecutions before being decided by a High Court judge.
The government also proposes that the home secretary notifies Parliament of any extension beyond 28 days with a requirement to provide a statement on the case. Parliament would have the option to debate the detention.
Separately, the government's terrorism watchdog would include these detentions in his annual report.
OPTION TWO: TAKE THE POWERS BUT HOLD THEM IN RESERVE
Under the second option, powers for extended detention would be taken along with the safeguards - but not brought into force without future Parliamentary approval. This would mean ministers would have to seek approval of both the House of Commons and Lords in a future specific case. The government says this is less practical because it could lead to a major debate on the policy in the middle of a national emer
OPTION THREE: USE EMERGENCY POWERS
Liberty, the human rights group, has proposed ministers opt for the third option using existing powers under the Civil Contingencies Act. Under this legislation, detention without charge can be extended for a further 30 days if the prime minister declares a state of emergency. At the end of a state of emergency, the detention time limit returns to 28 days.
OPTION FOUR: CONTINENTAL SYSTEM
The final option would be a major change in the legal system with the introduction of judge-managed investigations. Under this system, specialist judges would be assigned to a case after a suspect has been held for the first 48 hours.
The judge would oversee the investigation and, the government says, reflect the rights of the suspect as well as the needs of the investigation. Similar legal models are used in France and Spain.