The British government has been strongly criticised by a senior 26-County judge for failing to co-operate with an inquiry into bombings in Dublin in 1972 and 1973.
British collusion is suspected in the attacks, which were also blamed on unionist paramilitaries.
In his second report, Justice Henry Barron revealed that British authorities repeatedly stalled in responding to his requests for information relating to the attacks, which killed three and injured almost 200.
He said that on some occasions, the authorities in Britain failed to reply to requests for information and documentation, while there were also delayed replies to other communications.
Two car bombs exploded in Dublin city centre in December 1972 as the Dublin paraliament debated repressive anti-republican legislation.
Justice Barron said some aspects of the 1972 attack which were “not characteristic of loyalist subversive groups of that time”.
“In addition, the political context in which the attacks took place has led to speculation that members of the British army or intelligence services may have instigated, assisted with or even carried out the attacks,” he said.
“Those features may be consistent with involvement by the British army or intelligence services in the bombings. However, the circumstances are not so unique or even unusual that they would reasonably exclude of other groups.”
Therefore, the judge concluded that “while suspicions [of collusion] linger, evidence has not been forthcoming to take it beyond that”.
An Oireachtas [parliamentary] sub-committee has been appointed to consider the contents of the report and is likely to hold a series of hearings starting at the end of January.
Justice Henry Barron’s first report investigated collusion between British forces in the 1974 Dublin and Monaghan bombings, which killed 33 people and an unborn child.
Greg O’Neill, lawyer for the Justice for the Forgotten group, expressed disappointment with the report.
Sinn Féin Dail leader Caoimhghin O Caolain said the British government must be forced to co-operate with inquiries on collusion.
He claimed it was abusing its special relationship with the Irish government in order to avoid international accountability for its actions in Ireland.
“The British government failed to co-operate with the first Barron Report on the Dublin and Monaghan bombings of 1974. They refused the invitation of the Oireachtas Committee which held hearings on that report,” he said.
“They have failed to act on the call of that committee, unanimously backed by the Oireachtas, to establish a form of inquiry into the Dublin and Monaghan bombings.
“They have failed to have a resolution to this effect passed in the Houses of Parliament as recommended by the Oireachtas Committee,” he added.