Mr Justice Barron has defended his assertion that the government in 1974 could have done more to help further the investigation into the Dublin and Monaghan bombings.
The judge's remarks at an Oireachtas committee follow the rejection of major elements of his report by Dr Garret FitzGerald, Mr Paddy Cooney and Dr Conor Cruise O'Brien, who were ministers when 33 people died in the bombings on May 17th, 1974.
Mr Justice Barron also said the disappearance of the Garda intelligence file on the bombing and the failure of the British authorities to provide original intelligence information had hampered his work.
In a question and answer session with members of the Oireachtas committee on justice, the judge said he could not say that British agents colluded with the bombers because he did not have evidence to support that.
"I would say that the report generally indicates that there was a high level of collusion operating in Northern Ireland at that time," he said.
However, this was not to say that there had been collusion in the particular case of the 1974 bombings. While a perception of collusion might ultimately prove correct, he said this did not provide sufficient grounds to conclude that collusion had taken place.
He also said it was "totally unrealistic" to expect that reasonable evidence of collusion could be assembled by a public inquiry.
Several members of the Justice for the Forgotten group attended the session.
Mr Justice Barron said that information about the internment of the alleged bombers obtained from the British government at meetings in September and November 1974 was "new information" not already known by the Garda.
"That piece of information never percolated to the Guards in 1974 ... To the inquiry it seemed that this was a matter that should have been taken up one way or the other." The judge also said there was uncertainty about the government's policy on the possibility of gardaí travelling to the North to interview suspects. There was a theory that RUC co-operation with the Garda would lead to demands by the RUC to interview suspects in the Republic, he said.
He said he was "handicapped" by the disappearance of the 1974 intelligence file from the Department of Justice. While many files were received, he said: "The ones which I would regard as the most important to the inquiry were missing."
He saw no point in following up the disappearance because he had no evidence about it. "To go further might have been impugning honesty which is something I did not want to do." On the response of the British authorities, he said that assurances of co-operation had been given to the Taoiseach and to the Justice for the Forgotten group.
Of a meeting with the then Northern secretary, Dr John Reid, the judge said: "We stressed we wanted to receive original intelligence documents, but we never got that." He said there was not sufficient information in the extracts from files that the British government sent to the inquiry. "To put it simply, we feel there was more information there than what we got." While the judge was given a lot a information about intelligence networks and how intelligence was gathered, he believed that one table he received had been prepared for the Bloody Sunday Inquiry.
While RUC arrests of loyalist suspects in May 1974 were said to follow "good intelligence", the judge said the Northern Ireland Office and the RUC failed to provide a satisfactory reply to his response for more information about that intelligence.