Omagh bomb victims today called for talks with Northern Ireland's chief constable over revelations that anti-terrorism intelligence was withheld before the atrocity.
They have written to Sir Hugh Orde seeking a meeting to discuss MI5's handling of a tip-off ahead of the "Real IRA strike" that killed 29 people.
Although Sir Hugh insisted the agency did not deprive his officers of anything during their investigation into the August 1998 massacre, he has resisted pressure to disclose if any information was held back before the bombing.
Allegations that MI5 failed to inform Special Branch of the threat emerged during an investigation into an FBI agent who infiltrated the "Real IRA".
Based on a tip-off from American trucking company boss David Rupert, who was working undercover within the dissident republican terrorist organisation, three suspected terrorists were arrested by police in the Republic in April 1998 but released without charge.
Mr Rupert had warned that terrorists based in County Donegal were planning a strike on either Omagh or Derry, but most likely Omagh, security sources had disclosed.
At the time police in the North, then the RUC, were aware that a planned terrorist organisation had been disrupted due to the MI5 tip-off, it has been claimed.
But sources said no trace could be found on their records of any intelligence from the security services that Omagh or Derry had been targeted.
Police only became aware after detectives involved in the Omagh bomb inquiry spoke to Mr Rupert and studied e-mails the agent had exchanged with his handlers in the FBI and MI5.
He had been the central witness in the successful conviction of "Real IRA" mastermind Michael McKevitt, who was jailed for 20 years in 2003 for directing terrorism.
After Sir Hugh deflected questions at a meeting of the Northern Ireland Policing Board on Wednesday, the Omagh Support and Self Help Group wrote requesting an urgent meeting.
PA