The pursuit of the suspected killers of Seamus Ludlow was blocked by unidentified elements in the 26 County establishment, Justice Henry Barron has found.
The Louth man was murdered in 1976 by a sectarian murder gang of locally recruited British soldiers and unionist paramilitaries, who had driven over the border to find a victim.
The forestry worker was abducted and shot dead while hitching a lift near Dundalk in May 1976. At the time, it was announced that Mr Ludlow was killed by the IRA, and no proper investigation was conducted into his death.
His family have now called for an independent public inquiry into his death and said the Barron Report had raised questions which now needed to be answered.
Published amid considerable chaos in Dublin on Thursday, the report found the police in the South took no action for nearly 20 years, even after two of those involved had admitted their guilt.
Despite being informed of the identities of the main suspects, the gardai made no attempt to interview them.
A nephew of Mr Ludlow said a public inquiry would reveal more about the murder and subsequent investigation and compel people to cooperate.
“There was a cover-up and it went to a very high level in the gardai at least,” said Michael Donegan. “Someone at a high level ordered the murder investigation to be curtailed,” he said.
The British government has refused to cooperate with this and other investigations by Justice Barron which have implicated members of the British Crown forces in collusion and murder.
The report draws few conclusions, but suggests that former Garda police commissioner Laurence Wren probably made the decision not to pursue the killers.
Donegan said the report did not go far enough.
“We don’t know who he [Barron] spoke to or who he tried to speak to. The people who haven’t helped him got off lightly because we don’t know who they are.”
The four suspects, all from the Killyleagh area of County Down, were eventually interviewed by RUC officers at Castlereagh in February 1998.
During interviews, Paul Hosking claimed he could not understand why he was being questioned, as he had already admitted to Special Branch officers in 1986/87 that he had been present at the murder.
Recounting the murder, Hosking told detectives in 1998: “We picked up this man, we gave him a lift because he was thumbing, and then they took him up the road and shot him.
“It was terrible. I have lived with this for years.”
Hosking denied involvement in the killing itself and claimed that another suspect, Samuel ‘Mambo’ Carroll, had shot Mr Ludlow.
He also recalled how one of the four gang members, James Fitzsimmons, had used his British Army identity pass at a checkpoint when entering the 26 Counties.
Under questioning, Fitzsimmons admitted that he drove the car used in the murder to Dundalk and back to Killyleagh following the shooting.
“We stopped. I don’t know, I don’t know to be honest with you,” he said.
“I just don’t know... I heard bang, bang, bang.
“It nearly took my ears off. It was awful loud.”
UDR soldier Richard Long and Carroll both denied involvement in or knowledge of the murder.
The most damning aspects of the Barron Report relate to the fact that gardai failed to seek permission to question the four suspects, despite being provided with their identities in 1979.
Barron suggested this might have been done in order to avoid a situation where Garda might feel obliged to reciprocate by allowing RUC officers to conduct interviews south of the border.
Mr Donegan said the family had been unhappy with the gardai’s treatment of them since the day Mr Ludlow had been murdered.
“There was no real respect from the gardai then and none since,” he added.
The family want “truth and justice, not compensation,” Mr Donegan said.
“A lot of apologies are called for, from gardai, the government and the British security forces.
“We are not interested in the killers any more - no-one is going to be charged.”