Garda Commissioner Martin Callinan has said there are "issues that need to be addressed" regarding the appearance of a serving member of the force in RTÉ's crime drama Love/Hate.
Detective Kieran O’Reilly, who has previously worked in undercover drug operations, plays a member of an elite unit cracking down on gangland criminals.
Commissioner Callinan said a report was being compiled by a senior officer on how Detective O’Reilly came to be involved in the production.
“I’m very aware of the programme and its huge audience, and at this point in time it’s not appropriate to comment - other than to say I had a discussion with some of my senior colleagues who viewed the programme,” he said.
Under the Garda Code, acting is not a prohibited extra-curricular activity and it is understood that Det Garda O’Reilly took part in filming while on official leave earlier this year.
“We’re of the view that there are issues that need to be addressed and a superintendent will review those issues now,” he added.
A spokesman for the Garda Representative Association said: “We will be watching closely to see what the outcome of this due process will be.”
If the investigation, led by a superintendent outside the Garda National Drugs Unit where Det Garda O’Reilly works, decides he has breached regulations he could face internal disciplinary measures.
The character played by the serving garda made his first appearance early in Sunday’s episode, posing undercover as drug addict and setting up a garda sting operation.
Later, he joins up with the senior detective leading the case against the rest of the main criminal characters.
His character is set to feature prominently in the remaining episodes in what is the fourth series of the hit show which drew over 800,000 viewers when it was broadcast on Sunday night.