A listening bug could have been placed inside the Vauxhall car that carried the Omagh bomb, according to a High Court document.

The sensational suggestion that a security agency may have listened to the bombers on their way to the town is contained in an affidavit submitted on behalf of the Omagh relatives.

The document drawn up by their solicitors calls for the release of “a recording or recordings made of transmissions from a covert listening device placed in the maroon Vauxhall Cavalier car used to house the bomb transported to Omagh on 15th August 1998, together with transcripts and notes relating to that recording”.

The affidavit says the basis for the suggestion that the car itself had been fitted with a listening device is a conversation with Panorama reporter John Ware.

The legal document claims that the reporter indicated to solicitors acting for the families mounting a civil case against five men from south Armagh that his inquiries had indicated that a note of conversations inside the car had been available to the security services.

“The basis for that belief is a conversation with Mr Ware who indicated that his inquiries revealed that some individuals in the relevant authorities had read transcripts that appeared to include telephone conversations of the bombers in the car that were one-sided. It was further alleged that those conversations stopped at the time the bomb detonated”.

Mr Ware explained why he hadn’t contained the allegation in his programme, broadcast last September, which revealed that mobile phone conversations between the Real IRA bombers had been recorded by the government’s secret listening station GCHQ.

“I didn’t include it in the programme because I was not satisfied that the source who told me this was in a position to actually know that information”, he said.

But the suggestion that the actual bomb car was fitted with a listening device before it set off for Omagh has strengthened the call from the families for an independent cross border inquiry into the bombing, which killed 29 people and unborn twins.

Michael Gallagher, whose son Aidan was killed in the explosion, said the suggestion that the vehicle had been fitted with a listening device by a security agency was devastating.

“You know, every month or two something emerges about Omagh which increases the suspicions that the security services knew about either the plan to bomb Omagh or the people involved before they set off.

“This is another startling point that can only be properly addressed in a cross border inquiry. John’s reports are absolutely credible so if someone did indicate this to him I would say there was substance to it.

“If there was a bug attached to the bomb car who put it there, MI5, the Garda, who?

“That’s just another of the many questions that now have to be answered”, he said.