Donald Tusk: 'It is important that Brexit remains a one-off incident'

He said Brexit must not be the beginning of a process which leads to further splits in the EU's "unique territory of freedom".

Mr Tusk's comments were made in a promotional 42-minute film produced to celebrate the history of the European Council.

The council president said: "The EU doesn't have any divorce experience. We were good at broadening, not at shrinking.

"I'm convinced, however, that we will turn the corner. But the real threat today - and I think it is not only my opinion - is the disintegration of Europe in the political and ideological sense.

"It is not a coincidence that those who question liberal democracy are the same ones who call for the break-up of the EU, because the EU today is not only a political organisation which restricts national egoisms, it is also a unique territory of freedom.

"For this reason it is important that Brexit remains a one-off incident and not the beginning of a process."

The film, which is being sent to EU leaders, includes complaints about Margaret Thatcher's stubborn resistance at the Fontainebleau summit which saw her win a rebate for the UK.

Foreign Secretary Boris Johnson has suggested that Theresa May should follow the example of Britain's first female prime minister in her negotiations with the EU over money as the UK negotiates its Brexit divorce.

Former French president Valery Giscard d'Estaing said: "It was a most irksome business. And Mrs Thatcher had taken a stance that was quite disagreeable for her partners."

Former council general secretary Niels Ersboll said: "Mrs Thatcher won at Fontainebleau. She won too much in my view. It was not a good decision, it created the basis for years, generations, of dissatisfaction on both sides."