A former senior Irish diplomat, Sean Donlon, has told a parliamentary sub-committee in Dublin that be believed there was British security force collusion in the 1974 bombings of Dublin and Monaghan.
``The British army has always had units and elements in it that engaged in dirty operations,'' he said on Wednesday.
Twenty-six died in a series of bombings in Dublin city and amother seven died in another attack in Monaghan town on the one night in May 1974, all of which were claimed by the unionist paramilitary UVF.
Mr Donlon said that people at a senior level in the British justice system during the 1970s were aware of collusion going on, and yet did nothing to stop it.
He pointed out that if the British security forces, even rogue elements, had colluded with those who planted the 1974 bombs, the Republic's sovereignty would have been breached by the British.
``It's tantamount to declaring war. Governments should be able to control rogue elements. For the sake of our national interest this should be investigated.''
Mr Donlon worked on the Northern Ireland desk at the Department of Foreign Affairs from 1971 to 1978. He told members of the justice sub-committee he was appearing before them after responding to a newspaper advertisement seeking any relevant parties to come forward.
Mr Donlon worked for the Department for 28 years until 1987. From 1974 to 1978 he was in charge of the Northern Ireland desk, a role which involved collating information on security issues in the North, particularly on collusion.
Despite this, High Court judge Mr Justice Henry Barron never invited him for an interview in the preparation of his report, which led to the parliamentary proceedings at which he appeared.
While getting the truth about the bombings would prove difficult during any public inquiry, Mr Donlon said, it would not be impossible. On the possibility that an Anglo-Irish cross-jurisdictional inquiry could be set up, he said: ``I would not give up hope.''
Mr Donlon said inquiries into matters of public concern often worked best when headed by an international neutral figure. If the British and Irish governments could agree terms for a cross-jurisdictional inquiry into the events of 1974, and if it were headed by a neutral figure, it might be very effective.
The chair of the inquiry might be given access to British files denied to Mr Justice Barron, he said. Conclusions could be arrived at based on information in the files, without their content being put in the public domain.
He had believed the Barron report would focus on collusion and that the actions or inaction of the gardai and government of the day would prove secondary. But the opposite was the case. However, part of the reason Mr Justice Barron had not reached stronger conclusions on collusion, and other issues, was because he had been denied access to 68,000 files held by the British.
Meanwhile, two former Irish government minister have criticised a new report on bomb attacks by loyalist terrorists on the southern side of the border one night 30 years ago.
Patrick Cooney, who was justice minister at the time, said some of the findings of an investigation headed by Justice Barron were ``not worth the paper they were written on''.
Mr Cooney's remarks followed the rejection by former taoiseach Dr Garret FitzGerald of the findings of the inquiry into the Dublin and Monaghan bombings of May 1974. Dr FitzGerald - foreign minister when the bombs went off - rejected the report's criticism of the government at the time.