Taoiseach Bertie Ahern said last night that it was now "absolutely essential" the British government co-operate fully with investigations into allegations of British collusion in loyalist attacks during the mid- 1970s.
He was speaking following publication of an Oireachtas subcommittee report into a number of atrocities, including the Miami Showband massacre.
The subcommittee's inquiry, which examined the findings of an earlier investigation by Mr Justice Henry Barron, concluded that "widespread collusion" between British security forces and loyalist paramilitaries lay behind a number of atrocities on both sides of the Border that claimed 18 lives.
The subcommittee of the Joint Oireachtas Committee on Justice said it was "horrified" that people employed by the British authorities to preserve peace and protect people were "engaged in the creation of violence and the butchering of innocent victims".
Seeking co-operation from the British authorities, the Taoiseach said the finding that they co-operated with loyalist paramilitaries in the mid-1970s was "deeply troubling".
Saying that he had been "in touch" with the British government on the issue yesterday, Mr Ahern said: "It is absolutely essential that the British government examine the findings of all of these reports, as well as the forthcoming MacEntee report [ into the Dublin and Monaghan bombings in 1974] and that it fully co-operates with all investigations into the serious issues that have arisen."
Minister for Foreign Affairs Dermot Ahern said last night's report showed clearly there was collusion.
Copies of the latest report, and three previous ones, were sent immediately to Northern Ireland Secretary Peter Hain, the Minister told journalists last night. He said Mr Hain had indicated the British government would offer every possible co-operation: "He did indicate obviously that it was at quite a far remove, 1975, in around that time."
The subcommittee considered Mr Justice Henry Barron's report - which was published in July - on nine terrorist attacks, including the bombing of Kay's Tavern in Dundalk, the Three Star Inn in Castleblaney, and the attack on the Miami Showband.
It said it believed that unless the full truth about collusion was established, and unless those involved admitted or were fixed with responsibility, then there could not be closure for the families.
In its report the sub-committee said there were acts of "international terrorism" involving collusion by British security forces.
The language used by the sub-committee - which has been relatively cautious in its judgments up to now - is significantly stronger than that used by Mr Justice Barron.