Gardai have launched an investigation into the golf event that was attended by former Agriculture Minister Dara Calleary and other public figures.
Deputy Calleary resigned after receiving public backlash over going to the dinner which had some 80 people present in Co Galway.
Senator Jerry Buttimer has also stood down as Leas-Cathaoirleach of Seanad Eireann.
Gardai have now said they are investigating the event, which allegedly breached health regulations.
A spokeswoman said: "An Garda Síochána is investigating an event that was held in Co. Galway on the 19th August, 2020 into alleged breaches of The Health Act 1947 (Section 31A-Temporary Restrictions) (COVID-19) (No.3) Regulations 2020, as amended.
"As this is an active investigation An Garda Síochána has no further comment."
It comes after Taoiseach Micheal Martin said that Dara Calleary had made a serious "error of judgement".
He said: "This morning Deputy Dara Calleary tendered his resignation as Minister for Agriculture, Food and the Marine, following his attendance at the Oireachtas golf dinner on Wednesday evening.
"His attendance at this event was wrong and an error of judgement on his part. I have accepted his resignation.
"People all over the country have made very difficult, personal sacrifices in their family lives and in their businesses to comply with Covid regulations.
"This event should not have gone ahead in the manner it did given the Government decision of last Tuesday.
"Dara Calleary, since he was first elected to Dail Eireann has been, and remains, a committed and dedicated public representative. This error of judgement was out of character.
"He has made the right decision for the country, particularly in the light of our continued efforts to supPress Covid-19."
