An ex-garda has alleged strict protocols were sometimes ignored
It is reported a significant number of innocent people had their phones tapped by gardaí.
The allegation was made by a former garda intelligence officer, who says it happened from the late 1990s to early 2000s.
The Irish Independent reports the ex-garda made allegations that strict protocols for placing wiretaps were sometimes ignored.
It claims the detective who raised concerns was offered a transfer out of garda intelligence.
Political correspondent with the Irish Independent Niall O'Connor, who wrote the story, has more details.
"We have found that over a course of nearly a decade, within what is known as the Monitoring Section within An Garda Síochána - the section tasked with intercepting and placing taps on people's phones - that in the course of that particular practice, a number of innocent members of the public unbeknown to them had their phones listened in to.
"This case very much centres upon a particular officer who took a lawsuit against the State, and settled against the State.
"He was senior figure within that monitoring section - he has said in court documents that over the course of nine or tens years, innocent people were getting caught up in the cross-fire... of wiretaps".
It is also claimed that a number of senior politicians also had their calls intercepted.
"A number of senior politicians - household names from both sides of the Irish Sea who have held every senior political positions - they also had their phone calls intercepted by officers.
"We have discovered that some very, very serious criminals... they have also had their calls intercepted.
"But what would be concerning I think is that you have a situation where innocent members of the public were having their private conversation listened in to by gardaí.
"In some cases it happened because of sloppy practice - a wrong phone number was given, it was a case of mistaken identity".
He says there is likely be some form of investigation into this.
"I would expect that members of the opposition will seek answers here", O'Connor adds.
This comes amid mounting scandals in the garda force.
A damning Garda Internal Audit Section interim report in March examined financial procedures at the Templemore college.
Auditors looked at the accounts between January 2009 and March 2016, when around €112m was spent.
The report found that no financial controls existed on a number of bank accounts linked to the college.
Garda Commissioner Noirin O'Sullivan has claimed there was no criminality involved in the misuse of funds.