The EU will be “defeated” in Brexit negotiations unless it maintains absolute unity, European Council president Donald Tusk has said.

The ex-Polish prime minister told the European Parliament the UK’s departure was the EU’s “toughest stress test” and it must not be divided at any costs.

“If we fail it then the negotiations will end in our defeat,” he told MEPs.

But one German MEP said the EU’s stance was “illogical, dangerous and unfair” and UKIP accused the EU of “extortion”.

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The UK is due to leave the European Union at the end of March 2019 and until Mr Tusk’s comments both sides have sought to avoid talking about victory, defeat and winners and losers in the negotiations.

In an update following last week’s Brussels summit where the Brexit process was discussed, Mr Tusk said he was “obsessed” with preserving the unity of the other 27 members.