Fianna Fáil has ramped up the pressure on Gerry Adams over his continued refusal to hand over the name of a senior IRA figure who may hold the key to solving the murder of prison officer Brian Stack.
The Sinn Féin president was warned he faces an "obligation" to provide any information to investigators that could assist the murder inquiry.
But the Louth TD refused to be drawn on the growing controversy last night, instead opting to re-release a statement he gave to the Dáil on the killing on December 7.
In the statement, Mr Adams said he would co-operate with gardaí in relation to the investigation - but repeated his view that people involved in the IRA should not be named.
"Progress was only possible on the basis of confidentially and trust," Mr Adams said in his statement that was rehashed last night.
"That is why no IRA people were named during any of these initiatives and why they should not be named today."
The controversy surrounding the Stack case was reignited after the Irish Independent revealed that gardaí have stepped up their investigation into the 1983 murder.
Detectives attached to the National Bureau of Criminal Investigation (NBCI) have begun a fresh round of interviews in a bid to determine the identity of the IRA figure who attended a 2013 meeting with the victim's sons Austin and Oliver Stack at an undisclosed location.
The brothers have been interviewed separately in recent weeks.
The pair provided detectives with information aimed at building a profile of the IRA figure, who was a trusted associate of Mr Adams at the time.
In a statement released yesterday, Austin Stack accused Mr Adams of continuing to compound his family's pain.
"The Stack family note that on several occasions Deputy Adams has publicly called on anybody who has information regarding the murder of my father to go to An Garda Síochána," Mr Stack said.
"His own reluctance to do just this seems to imply that he holds himself above the law and is willing to apply a different set of standards to himself than he would to any other citizen of this Republic."
Mr Stack also said his family had received many messages of goodwill, including from former colleagues of his father. "Brian Stack was not a solider and neither was he fighting in a war. Brian Stack was a chief prison officer, his job was to protect society by ensuring some of the most dangerous criminals to come before Irish courts served their time fully.
"This meant among other things stopping the flow of guns and explosives into Portlaoise Prison; Brian Stack was good at his job and was therefore targeted by the IRA for assassination."
Last night, Mr Adams came under further pressure.
Fianna Fáil said it was not acceptable for anybody to withhold information that could assist a live murder investigation.
"Every citizen faces such an obligation, whether you are a politician or not," Fianna Fáil's justice spokesperson Jim O'Callaghan told the Irish Independent.
It's understood the Stack case has been discussed in recent weeks at senior management level within An Garda Síochána, since Mr Adams sent an email to the Garda Commissioner with a list of four names who he said may have information in relation to the case.
Two of the individuals - TDs Dessie Ellis and Martin Ferris - were named in the Dáil under privilege. Both deny having any information relating to the case.
Detectives are conducting a fresh round of interviews with the family of murdered prison officer Brian Stack as they attempt to identify the senior IRA figure who admitted the terror group was behind the 1983 killing.