Speaking on Tuesday, relatives accused the British Govenment of withholding information about the atrocity, which claimed the lives of 29 people and two unborn twins.

Over the weekend, it was revealed intelligence officials were recording the bombers' mobile phone calls prior to the planting of the 1998 car bomb.

The revelation formed the basis of a BBC documentary on Monday evening.

Michael Gallagher - who lost his son in the Market Street bomb - has written to PSNI Chief Constable Sir Hugh Orde on the isue and is demanding action within a week.

"We feel that there may be a criminal act committed here, there could be the perversion of justice, there is a charge of withholding information about a serious crime," he said.

"We believe the intelligence services, the police service and those who work in law and order have responsibility and have to live up to that responsibility, and there has to be some degree of accountability. Until we do have that, we will have an intelligence service that is possibly out of control and a law unto itself," he added.

Another relative, Carol Radford said: "The whole point is to try to put the bad guys away, what is the point of gathering it (intelligence), if you are not going to use it? The Government can't walk away from this."

The Omagh relatives have been campaigning for a full public inquiry into the bombing.