Intelligence Services Commissioner Sir Peter Gibson, who was commissioned by Prime Minister Gordon Brown to investigate the circumstances of the 1998 tragedy, found information on the bombers was passed to police but could not have prevented the atrocity.

Twenty nine people were killed in the Co Tyrone town, including unborn twins.

Relatives of the deceased had called for the independent investigation.

In his report, published on Wednesday, Sir Peter said: ""I am satisfied that in the days surrounding 15th August and on the day itself, to the extent that any relevant intelligence was derived from interception, it was shared with RUC HQ and Special Branch South promptly and fully, and done so with the latter in accordance with procedures agreed with Special Branch South."

Mr Gibson also confirmed there was no evidence before him that police in the Republic had warned the RUC of a likely attack.

A BBC Panorama programme had claimed that intelligence officers had tracked the movements of the bombers' car and a scout car on their way to Omagh from the Republic on the day of the attack.

This was denied by Sir Peter in his detailed report, saying technology was not so well advanced in 1998 to so so.

Omagh bomb relatives are due to meet with Prime Minister Gordon Brown next month. They are calling for a cross-border judicial inquiry into the attack.

Reacting to Sir Peter's findings, Michael Gallagher, who lost a son in the atrocity, said: "We believe that mistakes were made and those mistakes should be examined and put right to give us a better chance of preventing any future attack and catching those responsible."

Relatives are currently involved in a civil case in the Republic against five men they believe were responsible for the bombing.

No-one has yet been convicted for the outrage.