Omagh was the biggest loss of life in a single attack in the Troubles
Relatives of some of the 29 people killed in the Omagh bombing have issued a fresh appeal for an inquiry.
The move came after a review of how intelligence on the bombers was handled was published on Wednesday.
Intelligence Services Commissioner Sir Peter Gibson said information had been shared with RUC Special Branch, but could not have stopped the 1998 attack.
The report said vital intelligence which could have prevented the Real IRA bombing had not been withheld.
In his report, Sir Peter said details from telephone intercepts were passed on "promptly and fully" and in accordance with proper procedures.
Only a summary of Sir Peter's report has been made public.
Twenty-nine people were killed when a Real IRA car bomb exploded in the town.
A BBC Panorama programme had claimed that intelligence officers based at GCHQ had monitored the bombers' phone calls, but had failed to pass information to RUC detectives hunting the killers in the days following the attack.
Following the programme last September, Prime Minister Gordon Brown commissioned Sir Peter to conduct a review of all intelligence material stemming from the bombing.
A spokesperson for Panorama said on Wednesday the programme had laid out "a series of important questions flowing directly from the knowledge that some mobiles had been intercepted, including whether the bombing could have been prevented".
"We stand fully by the Panorama programme - both the programme and Sir Peter Gibson's report raise many new questions of significant public interest about what happened before the Omagh atrocity and in the aftermath.
"Nowhere does the report or the Northern Ireland Secretary's statement deny that interception was being carried out by GCHQ or that any intelligence flowing from it did not reach the investigating officers.
"The thrust of the programme has therefore yet to be addressed - at least publicly - by the government."
Michael Gallagher, whose son Aiden was one of the 29 people killed in the atrocity, said he did not accept that the Panorama had unfairly raised people's expectations.
"We believe the BBC and John Ware actually highlighted something that we had concerns for, on both sides of the border, over a number of years," he said.
Mr Gallagher also said he did not accept that the Real IRA attack could not have been prevented.
"I think there was a large amount of high-grade intelligence available. The fact that GCHQ themselves were monitoring - live or otherwise - demonstrates that," he said.
In his report, 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."
Sir Peter also said there was no evidence before him that police in the Republic had warned the RUC of a likely attack.
He also dismissed the programme's claims that intelligence officers had tracked the movements of the bombers' car, saying technology was not advanced enough in 1998 to do that.