Controversy over an alleged shoot-to-kill policy in Northern Ireland caused grave implications to cross-border co-operation while Anglo-Irish relations suffered a "serious setback", newly-released files reveal.
The Republic's Justice Minister Gerard Collins told a special meeting of the Anglo-Irish Intergovernmental Conference in February 1988 that it was "impossible to exaggerate the seriousness of the shoot-to-kill policy".
Mr Collins said the meeting, at Stormont Castle in Belfast, was called in response to "very serious concerns" shared by all sides of political opinion.
It came after the British Attorney General made a public statement about the Stalker Inquiry.
Two senior UK policemen, John Stalker and Colin Sampson, investigated a series of incidents which resulted in the killing of three RUC officers - John Quinn, Allan McCloy and Paul Hamilton - in October 1982 and, weeks later, six unarmed nationalists.
Sean Burns, Eugene Toman and Gervaise McKerr were killed by police near Lurgan after the car they were travelling in allegedly crashed through a checkpoint in November 1982.
That same month Catholic teenager Michael Tighe was shot dead by police at a hay shed near Craigavon, while INLA men Roddy Carroll and Seamus Grew were shot dead near Armagh in December 1982.
The incidents became known as shoot-to-kill deaths and occurred during the darkest days of the Troubles in the mid-1980s.
Two highly-classified reports by Mr Stalker and Mr Sampson on the incidents have never been published.
The episode is detailed in previously-classified files released in Dublin under the 30-year rule. Files from 1994 have also been released in London and Belfast.
Mr Collins, referring to the Attorney General's intervention, wrote: "This statement, which admits evidence of obstruction of justice, amounts to declaration that in Northern Ireland, at any rate, the rule of law takes second or possibly third place to non-defined public interest and matters of national security.
"That's the scene as it is and how my government sees the implications of failing to prosecute."
During the special meeting with a series of Irish and British senior ministers, Mr Collins said: "It casts a dark shadow over the RUC and has the gravest implications for cross-border co-operation with the gardai, apart altogether from its impact on relations between the RUC and nationalists in Northern Ireland."
Mr Collins said that while he sympathised with RUC members who had been killed during the Troubles, he urged the British authorities to ensure that their security forces do not "descend to the level and methods of terrorists".
He also warns that if the RUC is known to have and be shielding officers who are "strongly suspected of serious crime", this will have an impact on community support in the Republic.
"There is also the question about the attitude of individual gardai. They will have reservations about making information available to the RUC if they are not fully confident about the use that may be made of it," he added. "The British Government has done very serious damage to confidence and co-operation and I believe there is a very great responsibility on it to put the matter right."
A memo from the Irish Government states that the failure to publish the report in full "contributes to the political problem by creating even greater unease".
"I think we all accept that this affair has seriously undermined the confidence among the minority in the administration of justice in Northern Ireland," it said.
Secretary of State Tom King said it was a police investigation and it was "not the practice" to publish these.
"The fact is that there is a public interest and national security responsibility. It is simply not practicable to make it public," he said. "Any such decision would require a very exceptional change in policy."