The detective heading the Omagh bomb investigation was challenged today to question a former spy who allegedly warned police a terrorist attack was planned.
Laurence Rush, whose wife Elizabeth was killed in the atrocity, asked Superintendent Norman Baxter late last year why he had not interviewed the ex-agent known as Kevin Fulton.
Fulton, who worked undercover in the IRA, provided crucial evidence for Police Ombudsman Nuala O'Loan's damning report on the original investigation into the August 1998 attack that left 29 dead.
But more than two years after her assessment, detectives have yet to ask the informer about what he told his handlers.
Mr Rush said tonight: "It's scandalous that they still haven't interviewed the main witness in Mrs O'Loan's report."
Fulton claims he told police three days before the Omagh bomb that terrorists were set to "move something" across the border into Northern Ireland in the next few days.
He also described meeting a known Real IRA man who was trying to acquire bomb-making equipment.
His information came after an anonymous phone call warned police an attack was planned for Omagh on the day of the bombing. This was never passed on to officers in the town.
In her report that contained scathing criticisms of former chief constable Sir Ronnie Flanagan's leadership, Mrs O'Loan insisted there was no reason to doubt Fulton's credibility.
No-one has ever been directly charged with the bombing, which was the worst single terrorist attack during 30 years of violence in Northern Ireland. But even though a new team has been brought in to hunt down the killers, Mr Rush was staggered that Fulton has yet to be questioned.
"Mrs O'Loan gave the families awful news that Fulton had given them warnings that should have been acted upon," he said.
"Two years later we are still appealing to police to interview this man."
Fulton, who is living at a secret location in England, spent more than 20 years ago working undercover for military intelligence, MI5 and Customs and Excise while in the Provisionals.
He has been locked in a long-running legal battle with the authorities over security arrangements. He claimed a deal had been reached to give him a property, a new identity and, eventually, some sort of cash settlement.
A Police Service of Northern Ireland spokesman said tonight that Mr Baxter was unavailable for comment.