Arlene Foster hits out at Dublin's stalling over Kingsmill files
Arlene Foster has accused the Irish Government of replacing "a soft border for terrorists" during the Troubles with a hard border when it comes to disclosing information about the past.
The DUP leader was echoing comments from a lawyer for families of those killed in the 1976 Kingsmill massacre.
Ten Protestant workmen were shot dead by the IRA in south Armagh.
Alan Black survived despite being hit by 18 bullets.
The relatives have requested access to information the Irish Government holds about weapons used, intelligence and the getaway van employed by the gunmen.
They accused the Garda and the Irish Government of only paying "lip service" to their concerns.
Alan Kane QC for the Kingsmill victims told a Belfast preliminary hearing the requests for information "have fallen on deaf ears".
Mrs Foster said she shared the "dismay and frustration" of the families who witnessed "limited progress on full disclosure from the Irish Government to the ongoing inquest process into the murders".
She added she had raised the issue directly with Irish Foreign Affairs Minister Charlie Flanagan.
"I have emphasised the importance of full disclosure from the Irish Government and all relevant bodies to both the Historical Investigations Unit and the inquest process, but I have also raised the particular issues involved in the Kingsmill case," she said.
"Clearly there was a soft border for terrorists during their brutal border campaign, but yet a hard border when it comes to documents, witnesses and information to the inquest process.
"This cannot continue and all that's possible must be done to ensure full disclosure in all relevant cases - and urgently for the Kingsmill inquest.
"The families involved must be afforded every opportunity to learn the truth of what happened and see action to bring the perpetrators of this atrocious sectarian attack to justice."
Mr Flanagan has since said that Dublin was in "direct contact" with the coroner conducting the inquest into the killings.
In addition, lawyers for the coroner are scheduled to meet representatives of the Republic's State solicitor's office soon.
A preliminary hearing is due to take place next month after prosecutors decided a man would not face prosecution over a palm print found on the getaway van used by the gunmen. Around 1,000 pages of new material were created by the most recent criminal investigation, lawyer for the coroner Sean Doran QC said.
Mr Kane said most of the information disclosed so far by the Republic was newspaper cuttings.
"A librarian could do it," he said.
Another lawyer characterised it as "pulling teeth", and said the official response had been "disingenuous".
Relatives were sceptical members of the Irish Government or Garda were taking meaningful steps, Mr Kane added.
He said: "They feel that this is but a window-dressing exercise that is being carried out by the authorities in the Irish Republic at the very last moment, knowing full well that this inquest is scheduled to take place in two months' time."
He added that a porous Irish border had allowed heinous massacres like Kingsmill to take place.
"That soft border which allowed that has been replaced by a hard border of failing to provide meaningful co-operation and disclosure to the inquest.
"The entire intelligence framework, the information concerning the suspect, information relating to weapons, issues relating to the palm print, those are just a few matters that we would certainly be wanting more information."
The Coroner's Court inquiry will resume in full in May.