In a farewell address during his final month at the helm of the EU, Tusk told an academic session at the College of Europe in Bruges that he believes it when an English friend tells him "that Brexit is the real end of the British Empire."
He said those who support Brexit seem to have a centuries-old vision of Britain from when it ruled an empire on which the sun never set.
He said, Reality is exactly the opposite. Only as part of a united Europe can the UK play a global role. His comments came as the British elections were getting into high gear, with Brexit as the main issue dividing the electorate.
He also called on Britons still seeking to stay in the EU not to give up hope.
British Prime Minister Boris Johnson has received a frosty reception in flood-hit areas of northern England after victims of torrential rains lashed out at his slow response in coming to survey the damage.
Johnson paused from campaigning to visit Stainforth in South Yorkshire, where residents were mopping up and military personnel were laying sandbags. Residents suggested he took his time.
One woman clutching a wheelbarrow alongside some troops told him: "You've not helped us. ... I don't know what you're here today for."
Johnson told reporters afterward that he understood the anguish of residents. He says that the shock of seeing your property engulfed by water is huge Opposition parties have criticized the government's response to flooding and it is rapidly turning into an election issue.
A former Conservative Party Cabinet minister says giving the party a majority in next month's election would be "disastrous" because it would allow Prime Minister Boris Johnson to take the U.K. out of the European Union without a deal.
David Gauke said Wednesday he would stand for re-election to the House of Commons as an independent as he seeks a majority that will block a hard Brexit and back a second referendum.
The former justice secretary told the BBC that a Conservative majority would mean leaving the EU "in effect on no-deal terms and that, I believe, would be disastrous for the prosperity of this country.'" The comments come a week after a former Labour Party lawmaker said party leader Jeremy Corbyn was "completely unfit" to lead the country.