Speaking for the first time since stepping down as president of the European Council, Mr Tusk said Brexit has been “one of the most spectacular mistakes” in the history of the European Union.
In an interview with The Guardian and six other European newspapers, he said Brexit was the “most painful and saddest experience” of his time in office.
Referring to the 2016 US presidential race and the Brexit campaign, Mr Tusk said a new element in politics was “the unprecedented readiness to lie on almost everything…to treat a lie as a justifiable tool to win”.
He said this “shameless” behaviour would have disqualified politicians 10 years ago.
Asked by The Guardian to specify who he had in mind, Mr Tusk said: “I don’t want to be too spectacular in my first interview…I have enough problems in my own country with professional and pathological liars.”
Just last month, Brexit secretary Stephen Barclay said he was “dismayed” by comments made about the UK by Mr Tusk.
He was referring to a speech in which Mr Tusk appeared to back Boris Johnson’s opponents ahead of the general election by advising campaigners not to give up on stopping Brexit.
Mr Tusk said the UK would become “an outsider, a second-rate player” after it left the EU, and said a friend who suggested it was “the real end of the British Empire” was probably right.
Mr Barclay said the speech showed there was a “total disregard for democracy from some of those at the top of the EU machine”.
Speaking on the second day of his job as president of the European People’s party, Mr Tusk told Spanish newspaper El Pais on Thursday that he felt Brexit “has been a lesson”.
“That is why no one in Europe is thinking seriously about an exit,” he claimed.
In October 2016, Mr Tusk said: “The brutal truth is that Brexit will be a loss for all of us. There will be no cakes on the table for anyone. There will be only salt and vinegar.”
While in February this year, he said: “By the way, I have been wondering what that special place in hell looks like for those who promoted Brexit without even a sketch of a plan to carry it (out) safely.”
Additional reporting by Press Association.