Sinn Fein was not represented by a TD at an event which saw the Freedom of Limerick City bestowed on murdered Garda Detective Jerry McCabe.
Maurice Quinlivan, a Limerick City TD, did not attend the landmark ceremony in the city, attended by Det McCabe's widow Ann on Thursday evening.
Det McCabe was shot dead in the village of Adare on June 7, 1996, in an ambush by an IRA gang.
Pearse McAuley, from Strabane, Co Tyrone, and Jeremiah Sheehy, Michael O'Neill and Kevin Walsh, from Limerick, were jailed for manslaughter by the non-jury Special Criminal Court.
McAuley had previously escaped from a prison in Brixton while awaiting prosecution over an IRA terror campaign in England.
His cellmate, senior IRA figure Nessan Quinlivan - brother of TD Maurice - also escaped.
A spokesman for Sinn Fein confirmed Mr Quinlivan was invited to the ceremony but said he was unable to attend as he was speaking in the Dail.
"The party was represented at the event by its councillors and Councillor Malachy McCreesh spoke at the event on behalf of the party," the spokesman said.
Fine Gael minister Patrick O'Donovan said the event was "the most important and significant event to be held in Limerick City" in many years.
It was, he said, a chance for the people of Limerick to say that the atrocity will never be forgotten and to formally recognise the Garda.
Speaking at the event, Det McCabe's wife Ann said it was a "very poignant" and "very proud day" for her family.
Gardai used the opportunity to make a fresh appeal for information about his murder 22 years ago this month.