Relatives of Omagh bomb victims today failed in their attempt to force the disclosure of any mobile phone conversations covertly recorded on the day of the atrocity.

Lawyers for the families involved in a civil action against five men they blame for the attack were seeking a court order for the production of tapes, transcripts or notes held by the British intelligence services.

Their application for access to top-secret information was based on a television documentary which claimed the Government listening agency General Communications Headquarters (GCHQ) monitored calls as the bomb team transported the car packed with explosives into Omagh, Co Tyrone where 29 people were killed in August 1998.

The allegations in the BBC Panorama programme led to Prime Minister Gordon Brown appointing Sir Peter Gibson to head up a three-month intelligence review.

As it was being carried out lawyers for the relatives, who are seeking multi-million pound damages, argued that a failure to disclose any intercept material would breach their right to a fair hearing.

Ruling on their application at the High Court in Belfast today, Mr Justice Morgan took into account Sir Peter's findings that there was nothing to suggest that a bomb attack was going to take place on August 15, or that Omagh was to be the target for any such strike.

The judge rejected claims that access to the recordings could help identify those involved in the telephone calls, pointing out that voice identification was found to be imprecise.

He said: "There was never complete certainty in the identification of a voice by listening to it or as to the real nature of the matters under discussion.

"Against that background it appears that disclosure for this reason is speculative."

Mr Justice Morgan added: "For those reasons I conclude that disclosure of these materials if it were to be ordered is likely to be of peripheral value in relation to the evidence in this case."

The issue of covert recordings emerged midway through the marathon trial of Michael McKevitt, Liam Campbell, Seamus McKenna, Colm Murphy and Seamus Daly. All five men deny responsibility for the Omagh bombing.

Lawyers for the families who are suing them claimed it would be an "affront to justice" if British intelligence services were not forced to reveal all relevant material.

Their application covered the Security Service, GCHQ, the Police Service of Northern Ireland and the Police Ombudsman.

But the intelligence agencies resisted, with their legal representatives claiming such recordings should not be handed over because their existence is merely public speculation.

Dismissing the application, Mr Justice Morgan also said he was satisfied that any disclosure by the Security Service to the PSNI or Ombudsman was made by the Director-General in accordance with the Security Service Act 1989, with restrictions on any further revelations.

He added: "That restriction was imposed by the Director-General in accordance with the obligations imposed upon him by the 1989 Act and by virtue of that Act attracts the same prohibition on further disclosure as applies to the Security Service."