A relatives' group of people killed and injured in the 1974 Dublin-Monaghan bombings said today they would be taking their case to the European Court of Human Rights.
Justice for the Forgotten (JFF) claimed they now have evidence to back up claims of collusion in the loyalist bombings which killed 33 people.
Mr Greg O'Neill, JFF solicitor, said: "We have moved beyond the suspicion and speculation.
"Having spent 11 years working on this case in different forms, the families and their lawyers are satisfied we have now prima facie evidence of collusion and participation in the bombings."
The group said it would be lodging two complaints with the European Court.
Firstly, that there is prima facie evidence the British Government in 1974 colluded in the bombings.
And secondly that the United Kingdom had breached its obligations under the European Convention on Human Rights by failing to co-operate with inquiries.
The group also repeated its demand for a full public inquiry into the bombings and criticised the Irish government of the time.
Mr O'Neill said: "We urge the Oireachtas to call for, and the Government to establish in this State, nothing less than a public tribunal of inquiry into those grave matters which require immediate investigation."
The Dublin bombs on May 17th, 1974, killed 26 people in three streets, including a pregnant woman.
The Monaghan bomb on the same day killed seven people.
A report last December by Mr Justice Henry Barron was critical of the Government at the time of the bombings and of the original garda investigation, but found no evidence of collusion at a senior level.
An Oireachtas committee on the Barron Report earlier this year claimed there were significant issues within the State that needed investigated.
It also found that the issue of collusion must be fully and properly investigated.
"In order to ensure that the rights of those murdered and maimed are ultimately vindicated we have instructed our lawyers to lodge two classes of complaints with the European Court," Mr O'Neill said.
He added: "They (the British government) have failed to act in a manner consistent with their international obligations to assist in the vindication of the right to life.
"They have shunned the very inquiry procedures that exist to protect and vindicate the right to life."
JFF said an investigation could only be conducted effectively with the participation of the British Government.
The group also said it would accept an invitation to meet officials from the British embassy to discuss the matter.
Mr O'Neill called for an inquiry to have the power to gather and publish further evidence that comes to light. It should also be able to inquire into matter relating to the bombings where there is an issue of public interest, he added.
PA