Ministers want to extend secret hearings to Britain's civil courts - so judges can deal with the increasing number of cases involving the intelligence services.
Justice Secretary Ken Clarke says it is the only way that judges can hear the testimony of spies working for MI5, MI6 or GCHQ. Getting them to give evidence in open court is not an option, he says.
A small number of courts already hold secret sessions to consider appeals from individuals facing deportation on evidence compiled by the security services. But how well does the system work? File on 4 hears evidence from lawyers who are concerned about the quality of some of the testimony given behind closed doors.
And the programme has learned of a growing number of closed justice cases being heard in Employment Tribunals where people are claiming they were sacked because they pose a risk to national security. Because the Tribunals are hearing evidence in secret, the claimants are unable to get further details of why they were dismissed.
Gerry Northam explores the operation of secret justice in British courts and asks whether its extension to more cases would be in the national interest.
Producer: David Lewis.