Update 8.50pm: The Justice Minister says he would be happy to meet the family of murdered prison officer Brian Stack.
The family of Mr Stack claim the Gardaí have had significant information on the murder for 27 years.
His son Austin claims Gardaí are protecting an IRA informant.
Justice Minister Charlie Flanagan says he's been assured by Gardaí there's no impediment to the investigation
"I'd be very happy to meet the Stack family again, said Minister Flanagan.
"I've known the Stack family in Portlaoise for decades and again I acknowledge the great level of public service that was given by Brian Stack and of course, he paid for that with his life in very brutal circumstances."
Earlier: Gardaí investigating the death of Brian Stack say they are satisfied they have been provided with all the relevant information from within the force.
The statement comes after the family of the IRA murder victim accused gardaí of protecting a republican informant at the expense of the investigation.
The prison officer was shot dead in 1983 and his family have accused a section of the Gardaí of withholding information about his killers.
"The investigators leading the investigation relating to the death of Mr Brian Stack are satisfied that they have been provided with all the relevant information they require from within An Garda Síochána," the Garda statement read.
"The investigation team is receiving the co-operation of all relevant sections within An Garda Síochána in order to pursue all possible lines of enquiry.
"An Garda Síochána maintains regular contact with the Stack family for the purpose of keeping them informed of any relevant developments in this investigation.
"An Garda Síochána is determined to bring the investigation into the death of Mr Brian Stack to a successful conclusion."
Speaking to Sean O'Rourke on RTÉ Radio 1 earlier today, Austin Stack, son of the late Brian, claimed that he was approached by a retired senior garda who told him an IRA informant had come to him and given him the names of people involved in the murder of his father.
Austin said that he was already aware of these names, but this third source provided further confirmation.
The retired Garda told him this information had been provided to Gardaí in 1990 and was on file.
Austin claims that when he spoke to the Gardaí in January 2016, the claim was denied.
"There was some very parliamentary language used towards us at that meeting and since then my mother has point blankly refused to meet with an Garda Síochána," he said.
"My view is that they are protecting an informant. That's the view that has been put to us by the investigation team.
'In our view, the information that's there could potentially lead to people being prosecuted if it matches up with the work that the Gardaí are doing since then'.
When asked by Sean if Austin knew the names of the individuals he was referring to, Austin said yes.
'I do, I know the individual. I'm quite confident that I know the names of the individual who drove the bike, who shot my dad and who sanctioned the murder," he said.
"There was one individual who was living in the 26 counties, another one is living in the United States."
The family sought a meeting with the Garda Commissioner for the last three years, Austin told Sean that they were 'essentially fobbed off'.
Asked have they sought a meeting with an Taoiseach Leo Varadkar or Justice Minister Charlie Flanagan, Austin said that they had not of late but that the family would be looking to pursue this now.
"I would be calling on the Taoiseach to keep the promises that his predecessor made to us, and I'd be asking Charlie Flanagan to keep the promises of his predecessor," he said.
'Enda Kenny and Frances Fitzgerald gave us that undertaking, they told us that the full rigours of the State would be put into this investigation and that situations involving an informant would not be allowed to hinder this investigation'.
The family of murdered prison officer Brian Stack says significant information was withheld by a section of the Gardaí investigating his killing.
It is claimed the infomation, which had come from an IRA informant and contained details of those responsible, had been on a file in Garda HQ since 1990.
Mr Stack's son, Austin, wants the Taoiseach to demand answers from the Garda Commissioner.
He is also looking for full access to all files.
Brian Stack was shot in Dublin in March 1983 and died 18 months later.