Phil Hogan has resigned as EU trade commissioner.
It comes after days of increasing pressure following his attendance at an Oireachtas Golf Society dinner earlier this month.
Dara Calleary resigned as agriculture minister and Senator Jerry Buttimer as Leas-Cathaoirleach of the Seanad for attending the same event.
In a statement, Mr Hogan said: "It was becoming increasingly clear that the controversy concerning my recent visit to Ireland was becoming a distraction from my work as an EU Commissioner and would undermine my work in the key months ahead.
"I deeply regret that my trip to Ireland - the country that I have been so proud to represent as a public servant for most of my adult life - caused such concern, unease and upset.
"I have always tried to comply with all relevant COVID-19 regulations in Ireland and had understood that I had met with all relevant public health guidelines, particularly following confirmation of a negative COVID-19 test.
"I reiterate my heartfelt apology to the Irish people for the mistakes I made during my visit.
"The Irish people have made incredible efforts to contain the coronavirus, and the European Commission will continue to support you, and all EU member states, in defeating this terrible pandemic.
"Let me say from the heart that I fully appreciate and recognise the challenge presented by the COVID-19 pandemic to our society and the global economy.
"As European Trade Commissioner, I have been at the frontline of the European Union's response to the crisis.
"I recognise and appreciate the devastating impact of COVID-19 on individuals and families, and I fully understand their sense of hurt and anger when they feel that those in public service do not meet the standards expected of them.
"It is important to state that I did not break any law.
"As a public representative I should have been more rigorous in my adherence to the COVID guidelines."
Composite image of (left to right) Green Party leader Eamon Ryan, Fianna Fáil leader Michael Martin and Fine Gael leader Leo Varadkar. Pictures: RollingNews.ieTaoiseach Micheál Martin, Tánaiste Leo Varadkar and Transport Minister Ryan have said they "acknowledge the resignation".
In a joint statement, the Government party leaders said: "While this must have been a difficult decision for him personally, we believe that it is the correct course of action given the circumstances of the past week.
"We all have a responsibility to support and adhere to public health guidelines and regulations.
"We all must persevere in our efforts against COVID-19.
"Former Commissioner Hogan has served Europe and Ireland with distinction.
"The Government will consider his replacement in due course."
And European Commission President Ursula von der Leyen said: "Commissioner Phil Hogan has submitted his resignation. I respect his decision.
"I am very grateful to him for his tireless work as a trade commissioner since the start of this mandate and for his successful term as commissioner in charge of agriculture in the previous college.
"He was a valuable and respected member of the college. I wish him all the best for the future."
