The British government has been asked for a “concrete response” concerning information it might have relating to the Dublin-Monaghan bombings.

Minister for Justice Charlie Flanagan said that he and Tánaiste Simon Coveney met British cabinet office minister David Lidington and Secretary of State for Northern Ireland Karen Bradley in London last week. The meeting was arranged through the British-Irish Intergovernmental Conference.

Speaking at a commemoration to mark the 45th anniversary of the bombings, Mr Flanagan said: “We were clear in our call for urgency in the progressing of this matter and the need for a concrete response from the British government.”

Thirty-four people were killed when bombs detonated in Dublin and Monaghan on May 17th, 1974, marking it among the worst atrocities of the Troubles.

Justice for the Forgotten, which was set up to campaign on behalf of the victims, has long suspected loyalist involvement in the killings. In particular it suspects a loyalist group, the Glenanne Gang, with the collusion of the Ulster Defence Regiment and the RUC.

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One of the 26 killed by the Dublin bombings in May 1974 lies covered on the path on South Leinster Street (Nassau Street), Dublin, with the remains of the bombed car smouldering in the background. Photograph: Tom Lawlor

Dublin bombings: a car burns on South Leinster Street after one of the explosions in the city in May 1974. Photograph: Tom Lawlor

To date all attempts to get the British government to open its files relating to the bombings have been unsuccessful.

An all-party Oireachtas motion calling for Britain to allow an independent judicial figure examine the papers was passed, but nothing has come of it.

“I know that you are frustrated that these motions that they have not been adequately responded to, but can I reassure you that we won’t be giving up in our efforts,” Mr Flanagan told relatives gathered at the monument to the victims in Talbot Street on Friday.

Mr Flanagan said he was also determined that progress should be made in dealing with the legacy of the pasts that were agreed as part of the Stormont House Agreement.

Dark days of the Troubles

“I am hopeful that the all-party talks will lead to a successful outcome leading to the re-establishment of the powersharing institutions in Northern Ireland,” he said.

“Dealing with the legacies of the past will be one way to honour the memory of all of those killed in the dark days of the Troubles including the victims of the Dublin-Monaghan bombings.”

The gathering at the monument in Talbot Street, where one of the four bombs exploded was addressed by novelist Julieann Campbell who is a niece of Jackie Duddy, the first person to be shot dead on Bloody Sunday.

Ms Campbell said the world now knows his uncle was an innocent man who had been shot in the back.

“We remain steadfast in the rule of law, believing that the truth should be reflected in the history books,” she said. “Like you, we have put our faith in the justice system and like you, we have been let down time and time again.”