Political reaction: The victims and survivors of the Dublin/Monaghan bombings were "badly let down" by the Republic's own institutions, Labour TD Mr Joe Costello, said last night.
He said the four-year investigation had failed to answer the key questions that have existed for three decades.
The 1973 Fine Gael/Labour coalition must be criticised for its "utter failure" to ensure that the bombings were properly investigated by the Garda "in the manner that they merited".
"The principal conclusion that must be drawn from a preliminary examination is that the victims and survivors of the Dublin and Monaghan bombings were very badly let down by the institutions of the State.
"Even after the comprehensive inquiry undertaken by Mr Justice Barron over a period of several years, it will be a great disappointment to everyone, but most of all to members of Justice for the Forgotten."
Mr Costello, the Labour Party's justice spokesperson, said it was clear from the report the Garda investigation into both bombings had been "totally inadequate".
"There did not appear to have been any real determination on the part of the authorities to see those responsible brought to justice. Even allowing for the very difficult conditions in which the gardaí were operating at the time, the account of the investigation is a sorry chapter of shortcomings and failure.
"The conclusion of the report that it is likely that there was collusion between those responsible for the bombing and members of the RUC and UDR is truly shocking, if not altogether surprising in view of the evidence suggesting this produced by the media over the years.
"While the search for the truth must continue, and while the sub-committee now established to consider the report will do everything possible to secure the truth, we all have to face the shocking prospect that we may never know the full story behind these shocking events."
The Fine Gael leader, Mr Enda Kenny, issued only a holding statement pending a detailed study of the investigation carried out by Mr Justice Barron.
Sinn Féin Cavan/Monaghan TD Mr Caoimhghín Ó Caoláin described the findings "as an indictment of successive Irish and British governments.
"It exposed that the handling of the investigation of the massacre by the authorities in the 26 Counties was appalling, and that, in the words of the report, the government of the day 'showed little interest'."
He said the investigation was "a tribute to the dedication of the survivors and the bereaved of the Dublin and Monaghan bombings" who formed the Justice for the Forgotten Committee in the early 1990s.
The investigation pointed to the involvement of agents of the British armed forces in the bombings.
"The British thwarted any proper investigation of the bombings. They failed to co-operate properly with Judge Barron.
"Equally serious is the report's scathing criticism of the role of the authorities in this State. The Garda investigation was totally inadequate, and was compromised by the close links between the Garda and elements of British intelligence, including British agents within the Garda.
"Successive governments were content to preside over a conspiracy of silence on all of this. It is appalling that when evidence was shown to the Irish government that the British knew the identity of the bombers, they showed little interest."
Green Party leader Mr Trevor Sargent expressed "shock" at the findings "which indicate a distinct lack of concern on the part of the government at the time following the worst atrocity in the history of the State.
"On top of government's lack of interest, the investigation was thwarted by the reliance on British forensic laboratory facilities. Given that British authorities are strongly suspected of collusion in these appalling crimes, it only adds to these suspicions that the British have failed to fully co-operate with the Barron investigation."
Despite the passage of 30 years, he said the State should use its current forensic laboratory facilities to examine any material held since the bombings.
