PLANES from the UK will not be able to land in the EU if Brexit “goes wrong”, Jean-Claude Juncker has warned.

The European Commission president also mocked the UK’s negotiating strategy as he addressed a public meeting in Germany. Laughter broke out as he referenced UK demands for the EU to help devise workable Brexit proposals.

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“Sometimes I have the impression that the British think it’s us who are leaving Britain, but it’s exactly the other way around,” he said at the event on Monday evening. He went on: “What will happen with air travel in Europe. If everything goes wrong then British planes will no longer be able to land on the continent. People didn’t know that, and they should probably have been told in advance.”

In Strasbourg yesterday Juncker issued a fresh warning to May there must be agreement on the Irish border if she wants a Brexit deal. Despite the rejection of key elements of the Prime Minister’s Chequers blueprint at last month’s summit in Salzburg, he insisted the EU still wanted an agreement.

However, addressing the European Parliament ahead of the next EU summit in Brussels later this month, he stressed the EU would not compromise on its principles.

“When it comes to the border between the Republic of Ireland and Northern Ireland, we are sticking to the point of view we have expressed so many times – Ireland first.”

The summit on October 18 to 19 has been billed as the “moment of truth” when it will become clear whether it is possible for the two sides to do a deal.

May has said the Government is working on new proposals to resolve the issue of the border – ensuring there is no need for the return of “hard border” controls.

The parliament also heard renewed criticism of Foreign Secretary Jeremy Hunt over his comparison of the EU to the former Soviet Union. Manfred Weber, the leader of the main centre-right grouping in the parliament, said Hunt needed to apologise.

Meanwhile, in an interview with the Daily Telegraph, DUP leader Arlene Foster outlined her belief that the Good Friday Agreement was not untouchable. She said: “It has been deeply frustrating to hear people who voted Remain and in Europe talk about Northern Ireland as though we can’t touch the Belfast Agreement. Things evolve, even in the EU context. There has been a lot of misinterpretation, holding it up as a sacrosanct piece of legislation.”

Her remarks provoked fury on both sides of the Irish border. Robin Swann, leader of the Ulster Unionist Party, said: “Arlene Foster’s comments on the Belfast Agreement are strategically short sighted.”

Mary Lou McDonald, the leader of Sinn Féin, said that Foster’s remarks revealed “a reckless disregard for the peace process, prosperity and progress”.