The Irish government has insisted it will not stymie efforts to find closure for Kingsmills massacre victims.
Ten Protestant textile workers were gunned down during an IRA roadside ambush in South Armagh in January 1976.
Relatives of some of those killed have threatened to pull out of an inquest if legal authorities in the Republic do not co-operate.
They are seeking details from the Garda about the weapons used, intelligence and the getaway van employed by the gunmen.
A statement from the Irish justice department said: “Any suggestion that there is an unwillingness by the Irish government to assist the inquest or stand in the way of closure for the victims’ families would be unfounded.
“The Irish government has given its commitment to co-operate to the greatest extent possible, within the law, with the inquest and, in fact, has taken unprecedented legal measures to facilitate that co-operation and to deliver upon its commitment.”
It said the government took the “unprecedented” step of producing domestic legislation to facilitate legal co-operation with the inquest.
“This legislation facilitated the transfer of significant evidential material by An Garda Siochana to the Northern Ireland coroner.
“The Irish authorities have continuously sought to cooperate with the coroner and his legal team as part of an ongoing legal process.”
The factory workers were travelling home from work when their minibus was stopped and they were shot
The attack was planned from the south and four weapons were recovered there. Victims’ relatives are seeking more details from the Garda.
Commissioner Noirin O’Sullivan says she cannot direct an officer to give evidence to the inquest without new legislation.
However lawyers for the families say O’Sullivan could ask her officers to voluntarily attend. Alan Kane QC for the families said PSNI officers attended the Smithwick Tribunal in Dublin on this basis.