The commission of investigation into the Dublin and Monaghan bombings has found no evidence of collusion in the winding down of the Garda investigations into the atrocities in May 1974.
The final report of the commission drawn up by its sole member, Patrick MacEntee SC, was published by the Government last night.
A total of 33 people - including a pregnant woman - died and 300 were injured when four car bombs exploded in Dublin and Monaghan. It was the highest death toll on a single day during the Troubles.
No organisation claimed responsibility but loyalist paramilitaries were blamed and there have been persistent, but unproven, allegations that elements within the British military colluded in the atrocities.
An inquiry by Mr Justice Henry Barron reported in 2003 that it was likely that members of the UDR and RUC knew of preparations to bomb Dublin and Monaghan, but that there was no evidence of collusion. The Barron report was also highly critical of the Garda investigation into the bombings.
The commission of inquiry was established to investigate and report on why the Garda inquiry was wound down in 1974, why the gardaí did not follow up a number of alleged leads and whether collusion was involved.
"The commission is satisfied that there is no evidence available to it which is capable of establishing any connection between the collusion alleged and the 'winding down' of the Garda investigations into the Dublin and Monaghan bombings," concluded Mr MacEntee.
He also examined claims a white van with an English registration plate was parked outside the Department of Posts and Telegraphs in Portland Row and was later seen parked in the deep-sea area of the B&I ferry port in Dublin, and the subsequent contact made with a British army officer on a ferry boat leaving that port.
He found that gardaí had investigated the matter and concluded that the driver of the white van was "in no way connected" with the bombings. He also interviewed a British army corporal allegedly sighted in Dublin at the time of the bombings and concluded that the man had no connection with the bombings and that the gardaí had followed up the appropriate leads.
However, the commission said it was hampered by inadequate information, including the loss or destruction of an unquantifiable amount of Garda documentation relevant to the investigations.