He was speaking after talks with Irish premier Leo Varadkar in Brussels, according to BBC.
Brexit-backing MPs reacted with anger to the comments, accusing Tusk of "arrogance."
Downing Street said it was a question for 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.
And at the end of their press conference, Varadkar was picked up by the microphones telling Tusk: "They'll give you terrible trouble in the British press for that."
Tusk nodded at the comment and both laughed.
Former UKIP leader, and now an independent MEP, Nigel Farage, tweeted back at Tusk: "After Brexit we will be free of unelected, arrogant bullies like you and run our own country. Sounds more like heaven to me."
Commons leader Andrea Leadsom, who also campaigned for Britain's exit from the EU, said Tusk should apologize for his "disgraceful" and "spiteful" comments.
"I'm sure that when he reflects on it he may well wish he hadn't done it," she told BBC Radio 4's World at One.
The Democratic Unionist Party's Brexit spokesman Sammy Wilson said, "This devilish Euro maniac is doing his best to keep the United Kingdom bound by the chains of EU bureaucracy and control.
"It is Tusk and his arrogant EU negotiators who have fanned the flames of fear in an attempt to try and overturn the result of the referendum."
But Sinn Fein President Mary Lou McDonald backed Tusk, arguing that it was the position of "hardline" Brexit-supporting MPs like Boris Johnson and Jacob Rees-Mogg that was "intemperate" and "untenable."
"They are people who have acted with absolute contempt for [Ireland], utter disregard for the experiences of Irish people, north and south, with utter disregard for the peace process that has been collectively built over decades," she added.
Tusk began his remarks by telling reporters there were 50 days to go until the UK's exit from the European Union.
"I know that still a very great number of people in the UK, and on the continent, as well as in Ireland, wish for a reversal of this decision. I have always been with you, with all my heart.
"But the facts are unmistakable. At the moment, the pro-Brexit stance of the UK prime minister, and the Leader of the Opposition, rules out this question.
"Today, there is no political force and no effective leadership for Remain. I say this without satisfaction, but you can't argue with the facts."
Theresa May – who supported the UK staying in the EU during the 2016 EU referendum but has always insisted that Brexit must be delivered because that was what people voted for – is due to arrive in Brussels on Thursday to seek legal changes to the withdrawal deal she signed with the EU. She hopes these changes will help her get it through the UK Parliament.
Tusk said that the other 27 EU members had decided in December that the withdrawal agreement was "not open for renegotiation".
He said, "I hope that tomorrow we will hear from Prime Minister May a realistic suggestion on how to end the impasse.... following the latest votes in the House of Commons."