EU chief Donald Tusk has dubbed Brexit one of the “saddest moments” in Europe’s recent history.
The European Council president also said that the thought of Britain leaving the EU makes him “furious”.
The former Prime Minister of Poland made the comments in an acceptance speech for an honorary membership of the University College Dublin’s law society.
He said: “I don’t like Brexit. Actually, that’s an understatement. I believe Brexit is one of the saddest moments in 21st century European history. In fact, sometimes I am even furious about it.”
Later, he added: “The most tragic moments in our history in Europe is because of ideologists.
“This is why we always prefer pragmatism in politics rather than grand visions.”
Mr Tusk went on to say that Brexit is one of a number of reasons to be concerned about the potential for a “gloomy and for sure spectacular show of another European disunion.”
He cited the questions Brexit has raised over the future arrangements for the Irish border as one of the areas where he saw a “dangerous potential for conflict.”
“Here in Dublin, and in Belfast, today, on the 20th anniversary of the Good Friday Agreement, thousands of people are looking with concern and anxiety to the future of the peace process after Brexit,” noted the European Council President.
Mr Tusk told the audience at University College Dublin that the issue was at the top of his agenda, saying: “This year I will about Brexit mainly unfortunately.
“It means instead of integration I will be dealing with disintegration, in fact. By this I mean some kind of damage control process.
“My main focus will be to eliminate, or at least to reduce, negative side effects of Brexit with the Irish question, of course, at the centre of my attention.”
Mr Tusk also made a pointed reference to immigration in the Brexit debate when told the Dublin audience: “You became a country of immigration for the first time, receiving more people proportionately than the UK. Yet nobody ever hears of any problems on this issue from Ireland.”
Despite speaking out so strongly against Brexit, the European Council President was keen to stress he was not a European federalist.
He said: “I’m really obsessed with European unity. But at the same time, I’m not a federalist.
“I don’t believe in one European nation or one European super state.”