European Council President Donald Tusk has spoken of a “special place in hell” for “those who promoted Brexit without even a sketch of a plan of how to carry it out safely”.
He was speaking after talks with Irish premier Leo Varadkar in Brussels.
Brexit-backing MPs reacted with anger to the comments, accusing Mr Tusk of “arrogance”.
Downing Street said it was a question for Mr Tusk “whether he considers the use of that kind of language helpful”.
The prime minister’s official spokesman said: “We had a robust and lively referendum campaign in this country. In what was the largest democratic exercise in our history people voted to leave the EU.”
He added that everyone should now focus on delivering that.
Mr Tusk’s Twitter account tweeted his comments immediately afterwards: