IRA evidence at the Birmingham bombings inquest has raised hopes that republicans could shed light on the Kingsmill massacre, a coroner has said.
A former Provisional recently named four people he claimed were involved in the Midlands pub attacks in 1974.
The Kingsmill inquest is examining the shooting dead of 10 Protestant men by republicans in South Armagh in 1976.
The coroner, Judge Brian Sherrard, said: "It has given me some cause for hope, perhaps, that the Birmingham inquest was the recipient of such valuable... information. I am at a loss as to how those who would engage in this type of activity would not wish to take the same approach to this inquest."
No one has ever been convicted of the killings.
Relatives of the victims want a dead suspect whose identity has been protected to be named, and that is the subject of legal discussions.
The coroner appealed for any individual or organisation involved in the killings to come forward, including those who performed operational or organisational roles.
The textile workers were shot when their minibus was ambushed outside the village of Kingsmill on their way home from work. Those on board were asked their religion, and the only Catholic was ordered to run away. The killers, who had hidden in hedges, forced the 11 remaining men to line up outside the van before opening fire.
Alan Black was the sole survivor, despite being shot 18 times.
Colin Worton, whose brother Kenneth was one of those who died, said: "Here again we are on a different planet because we were always led to believe the IRA had gone away but now we understand they are still intact whenever they came back and gave information into the Birmingham court. Why are they not doing it on this side of the water? I don't know."
He said nobody had the power to make people come forward. Mr Worton said the dead suspect should be named, adding: "It shouldn't be terrorist-led, this inquiry. We shouldn't be beholden on them. The security forces know each and every one that took part."
In his evidence to the Birmingham inquests, the then IRA head of intelligence in Ireland, Kieran Conway, described the victims' deaths as "accidental", in an "operation that went badly wrong".
Towards the end of evidence at the hearings, a former IRA member named four people he claimed were involved in the bombings. The man, identified in court only as Witness O, said he had been authorised to give the names by the current head of the IRA in Dublin.