Minister for Foreign Affairs Simon Coveney has ordered an investigation into a gathering of officials in his department in June 2020, in the aftermath of Ireland winning a UN Security Council seat.
The investigation will be undertaken by the new Secretary General in the department, Joe Hackett.
An image which was shared on social media at the time shows a number of officials from the Department's UN Security Council campaign team gathered together posing for a photograph indoors.
Ireland was in Phase Two of its reopening plan at that stage, and Covid-19 regulations stipulated that people could only meet up to six others from outside their household in both indoor and outdoor settings.
A departmental spokesperson told RTÉ News that the report should be completed by the end of the month. The spokesperson added Mr Coveney ordered the investigation last Thursday.
Earlier, Tánaiste Leo Varadkar said he did not know if the celebrations with champagne in the Department constituted an illegal gathering, adding it was a matter for gardaí and not for Government.
He said politicians do not have the power to discipline civil servants and that it was a matter for Mr Coveney as to whether an investigation into the issue should be called for.
He said it was wrong that it occurred but that it was 18 months ago and while perhaps a further investigation is required, its also important to put it into perspective.
Last Friday, Mr Coveney told RTÉ's News At One programme that he would be willing to go before an Oireachtas committee to answer questions about the event.
"This was the 17 June 2020 and it was an evening when I, with the Taoiseach, was watching in the Department of the Taoiseach the vote in the UN that resulted in us gaining a seat on the Security Council after three or four years of campaigning to be there," Mr Coveney said.
"Unfortunately, in my Department, there were 20 or so officials who have been very much involved in that successful campaign and when the vote came through, they celebrated in a way that they shouldn't have. They let their guard down.
"I have to say they're all mortified by what happened now and that shouldn't have happened and the Department has apologised for it."
He said that he was back in the Department later that night and called in to the UN section where "people were at work".
"When I arrived, there certainly wasn't a party going on, that's for sure," he said.
He said that the group involved are "all mortified by what happened now."
It said "steps had been taken" after the team "briefly let their guard down" 18 months ago whilst celebrating Ireland's election to the council.