The gathering took place at Iveagh House while the nation was under strict lockdown rules.
Coveney's secretary general tweeted a photo from the gathering, which showed roughly 20 department officials drinking champagne. No social distancing or mask-wearing was in evidence.
A spokesperson for the Department of Foreign Affairs has now revealed that Coveney has ordered a report to be put together on the incident. It is expected to be finished by the end of the month.
"I was told by my team that there had been a photograph that was put up on Twitter by the Secretary General," Coveney admitted. "That clearly was not a good idea, but it had happened. I was told, I think, later on that evening. To be honest with you, that wasn’t my focus that evening at all. I didn’t know that there was an inappropriate gathering, albeit temporarily, after the vote at all. I didn’t know that had happened. I was told later on that a photograph was tweeted out and it was later on, I think late that evening after midnight, it was taken down. My Secretary General at the time acknowledged that it shouldn’t have happened and it was a momentary drop of our guard, I think was what he said."
Coveney said that he initially declined to investigate the gathering as he didn't feel "there was a need for follow-up."
UK Prime Minister Boris Johnson is currently under pressure to resign following the revelations of several similar social gatherings held at 10 Downing Street throughout the pandemic.