Pat Finucane Centre slammed over claims of RUC bomb and gun attack on Co Armagh pub
The Police Federation and an Ulster Unionist MLA have clashed with the Pat Finucane Centre (PFC) over its claim that the RUC carried out an attack on a Co Armagh bar during the Troubles.
They accused the PFC of a shameful slur against the force.
But the PFC strongly defended its stance because serving RUC officers were involved in the attack.
In the tweet on Wednesday, the PFC publicised a screening of the Glenanne Gang documentary Unquiet Graves at the Rock Bar in Granemore, Co Armagh, stating that the pub had "survived an RUC bomb and gun attack".
On June 5 1976, loyalists - believed to be members of the Glenanne Gang - threw a bomb into a bar filled with customers and shot through the windows.
The bomb only partially exploded and no one in the pub was injured, although one customer outside was shot and wounded.
It later emerged that three of those who carried out the attack were serving RUC members.
UUP justice spokesman Doug Beattie said: "The attack on the Rock Bar was carried out by terrorists, nothing more, nothing less.
"It was investigated by the RUC and evidence was sought to secure convictions for those responsible.
"There is no doubt that, during the course of the Troubles, a very small number of police officers broke the law and disgraced the force.
"This is true of any profession - be it doctors, teachers, accountants or lawyers," he said.
Mr Beattie said his party supported police officers who "stood between the terrorists and the terrorised".
The UUP MLA said that a campaign to "rewrite the history of the Troubles" was gathering pace with attempts made to portray the RUC as "the villains of the piece".
A total of 302 police men and women were killed during the conflict and 900 injured, he said.
"As a force they stood with incredible bravery, professionalism and a stoic defence of the rule of law.
"In doing so they no doubt prevented Northern Ireland slipping into a full scale civil war, and during the Troubles the jails were full of terrorists - both loyalist and republican - because of the dedication to duty of the men and women of the RUC," he added.
Defending the tweet, PFC spokesman Alan Brecknell said it was a fact that RUC officers were involved in the attack on the bar.
"At no point does Doug Beattie MLA actually mention that the gun and bomb attack on the Rock Bar was conceived and carried out in its entirety by serving members of the RUC, that a police vehicle and radios were involved, that one of those responsible was actually on duty and that one of those involved took statements from survivors in the aftermath," he said.
"Only one officer received a custodial sentence with the others receiving suspended sentences from a trial judge who admitted that sentences would be 'on a lower scale' because these were police officers trying 'to rid the land of pestilence'."
Mr Brecknell added that the UUP MLA "correctly points to the sacrifice made by many RUC officers and on this we have no disagreement".
Police Federation chairman Mark Lindsay also condemned the PFC's tweet.
"This is part of an overall attempt to demonise the RUC and rewrite history, putting an erroneous and scandalous slant on what actually happened," he said.
"It is a shameful slur on the heroic men and women of the RUC GC to counter vicious terrorism from both republican and loyalist sides who slaughtered thousands of innocent people.
"We will counter such propaganda at every opportunity to let the world know what decent people had to endure at the hands of evil doers."
Kenny Donaldson of Innocent Victims United (IVU) said the tweet by the Pat Finucane Centre - named after the lawyer murdered by loyalists - was "deeply concerning" and was "raw revisionist propaganda at its ugliest".
He said: "Whether the agitators were republican or loyalist terrorists or individual members of the security forces who dishonoured the code and engaged in criminal-based activity, IVU's stance has never and will never change - all criminal violence in the context of 'The Troubles' was wrong and without justification."
"Neither the RUC nor UDR planted bombs, nor did they corporately carry out shooting attacks. A small number of individuals infiltrated the police and army and followed their own ideological agendas contrary to the wishes of their colleagues and with no legitimacy."
Mr Donaldson added: "We stand by the tens of thousands of men and women who put a uniform on their back and prevented this place from transcending into a civil war situation. They are the heroes and martyrs within our society."