Tusk warns UK on harsh realities of Brexit

"The brutal truth is that Brexit will be a loss for all of us," he said, adding: "This scenario will in the first instance be painful for Britons."

Mocking a lead Brexit campaigner, foreign secretary Boris Johnson, who previously suggested Britons "could have their cake and eat it" - implying Britain could stay part of the EU's single market, while also restricting free movement of EU citizens - Tusk said: "To all who believe in it, I propose a simple experiment. Buy a cake, eat it, and see if it is still there on the plate."

He 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."

Tusk warned London not to expect much wiggle room on the four freedoms of the EU, and that it should not count on untangling the principle of free movement from access to the single market.

"There will be no compromises in this regard," Tusk said.

He said the EU 27 will negotiate in good faith, but they have to protect their interests.

He also offered an olive branch, saying London could still backtrack.

"In my opinion, the only real alternative to a 'hard Brexit' is 'no Brexit'. Even if today hardly anyone believes in such a possibility," he said.

Last week UK prime minister Theresa May said London would opt for a clean break from the EU, valuing control over immigration over and above access to the single market.

Her comments saw the pound fall further on the markets, but she has committed to launching the Article 50 exit procedures before the end of next March.

No fatalism

Tusk in his speech also called on EU leaders to resist fatalism or giving into populist forces.

"The most serious crisis of modern times is the weakening, if not the breakdown, of faith in the durability and purpose of traditional values, which are a foundation of the European Union and, more broadly, of the whole political community of the West," Tusk said.

"We must prove, however, every single day, that liberal democracy doesn't have to be a synonym of weakness," he said.

He pointed to the values which bind Europe together: human rights, civil liberties, freedom of speech and religion, free market and a competitive economy based on private property, reasonable and fair redistribution of goods, restrictions on power, tolerance and political pluralism.

"My generation knows this catalogue by heart," the former Polish prime minister said.

Recalling the Second World War, Tusk said the source of it "was the questioning of those values and treating national egoisms, the use of violence and the unlimited right of the stronger to dictate conditions for the weaker as the norm."

He said the threat today is the disintegration of Europe.

"It is no coincidence that very often those who question liberal democracy are the same ones who call for the break-up of the European Union," he warned.