The Irish Government has failed to respond to a request for a meeting with bereaved families and survivors of the Omagh bombing ahead of the first hearing of the inquiry.
Twenty-nine people, including a woman pregnant with twins, died after the dissident republican bomb exploded in the Co Tyrone town on August 15 1998.
Northern Ireland Secretary Chris Heaton-Harris ordered the statutory inquiry into the attack last year in response to a court judgment that directed the government to establish some form of investigation.
On February 21, the UK government published the terms of reference for the independent inquiry.
The first public hearing of the inquiry is due to take place at the Strule Arts Centre on July 30. An update on the progress made to date is expected to be provided during the meeting.
In a statement, John Fox of Fox Law, acting on behalf of 14 of the bereaved families and 10 survivors, said the families were “pleased with the progress made to date” but urged the Irish Government to “fully cooperate”.
He added that the Irish Government had not responded to a request for a meeting filed the day after the terms of reference were published, despite multiple attempts to follow up.
In a statement, Mr Fox said the Irish Government “has remained silent” since February.
He added: “The level of cooperation must provide the UK inquiry with full access to all materials held in the Irish State but also the ability to compel witnesses within the Irish state to give evidence.”
In his 2021 judgment, Mr Justice Horner directly recommended that the UK Government carry out an investigation into alleged security failings in the lead-up to the atrocity.
While having no jurisdiction to order the Irish Government to act on the matter, the judge urged authorities there to establish their own probe in light of his findings.
In February 2023, then Taoiseach Leo Varadkar pledged his governments full co-operation to the inquiry. During a visit to Belfast earlier this year Micheál Martin confirmed the government’s intention to co-operate, but said he did not think it made sense to have public inquiries on both sides of the border.
Mr Fox added: “Former Taoiseach, Leo Varadkar, had vowed his commitment to pass whatever legislation is required in the Dail, the bereaved families and survivors urge the current Taoiseach, Simon Harris, to honour this pledge.
“As we approach the first public hearing of the Inquiry, to take place just before the 26th Anniversary, the Irish Government is urged to fully commit to ensuring that their cooperation will enable the truth to be established.
“A full response and meeting with the Irish government had been requested several months ago and to date no response has been forthcoming.”
A spokesperson for the Department of Justice and Foreign Affairs said: “From the moment the British Government announced an independent inquiry into the Omagh bombing, the Tánaiste and Minister for Justice have been very clear that the State will engage fully with the work of the Inquiry.
“Officials from the Departments of Justice and Foreign Affairs are in ongoing contact with the Inquiry team to establish the precise nature of such cooperation and, noting that the intention is to work with an inquiry established in another jurisdiction, what mechanisms are in place to enable it and what further steps the State may need to take.
“We hope to be able to give further detail on this ahead of the scheduled first hearing of the Inquiry on July 30th.”