The Barron report on the Dublin-Monaghan bombings, published this evening, criticises the Fine Gael-Labour government of the day for its response to the atrocity.
Thirty-three people died in the bombings in May 1974.
The report says the government of the time failed to show the concern expected of it.
The report is also highly critical of the garda investigation which followed.
The inquiry found that vital forensic records had been lost and this carelessness reflected a belief amongst the gardaí that no one was ever going to be charged.
In terms of any possible collusion between security forces and loyalist paramilitaries north of the border, it says that it is not absurd to conclude that members of the army or police might have been involved in helping the bombers.
The report concluded it was likely that members of the UDR and RUC knew of the preparations to bomb Dublin and Monaghan.
But the report said there was no evidence of collusion between the bombers and the authorities in Northern Ireland.
The inquiry said on their reading of the evidence, this inference is not sufficiently strong.
They believe the bombings were provoked by moves to involve the Irish government in the administration of Northern Ireland through the FG agreement.
33 killed in 1974 bombings
Three car bombs exploded in Dublin city centre, on Parnell Street, Talbot Street and South Leinster Street.
It was a busy Friday evening in the capital: no warnings were given, and the explosions killed 26 people, including a pregnant woman.
A short time later, a bomb exploded in Monaghan town. Seven people were killed as a result of that explosion.
No one was ever prosecuted in connection with the bombings.