Pat and Irene Dignam - whose son John (32) was shot dead in 1992 - met members of the cold cases unit for the first time last week.

And the Portadown couple said HET officers appeared shocked that Garda hadn't investigated a report of their son's abduction in Co Monaghan.

IRA gunmen kidnapped the dad-of-two along with fellow Provos Gregory Burns and Aiden Starrs in June 1992.

All three, who were implicated in the murder of Portadown woman Margaret Perry, had been recruited by British Intelligence.

The trio were interrogated for a week by the IRA's notorious 'nutting squad' before being shot in the head and dumped on the border.

The Dignams say they have evidence an RUC inspector contacted southern counterparts after their son's disappearance to inform them he had been abducted in Castleblayney.

But the Irish Justice Department wrote to the couple last year saying the Garda had no evidence he'd been abducted in the Republic.

"They (the HET officers) were totally shocked to discover Garda hadn't investigated the case," said Mr Dignam.

"We showed them letters from the Irish Justice Department. They took the letters away with them, saying they would pursue the matter with the Garda. "

He said he also wanted HET officers to quiz Irish police about three houses - two near Omeath on the Cooley peninsular and the other near Kingscourt, Co Cavan - where the 'nutting squad' interrogated alleged informers.

He said Garda Special Branch would have recorded the fact the houses were being used by the IRA and that the records should still be available for inspection by the HET.

The couple, who were accompanied at the meeting by human rights campaigner Jane Winter, said they had confidence in the HET re-investigation of their son's murder.

"So far they have been open and frank with us. They have told us what they have done so far and what they are about to do now," said Mrs Dignam.

At the time, the IRA claimed all three had admitted working for the British and RUC.

Over the years allegations the three men were sacrificed by British Intelligence to protect the identity of the more important IRA double agent, Freddie 'Stakeknife' Scappaticci, have increased.

Earlier this year Police Ombudsman Nuala O'Loan launched a McCord-style investigation into allegations of state collusion in John Dignam's murder.