THERESA May’s trip to the continent has not gone well, with the Prime Minister finding herself a prop in the French presidential election and EU officials warning that Britain now faces a “dirty Brexit”.

Alain Juppé, one of the candidates to take over from Francois Hollande, said Brexit meant it was time to move France’s border with the UK back from Calais to Kent.

May, who has spent the last two days at her European Council meeting in Brussels, has made it clear the border is not for moving.

The Le Touquet treaty, signed in 2003, is the deal on the “implementation of frontier controls at the seaports of both countries on the Channel and North Sea.” It allows France to have passport control in Dover, and the UK have a checkpoint in Calais.

But it means anyone travelling through France to seek asylum in the UK is often stuck at the jungle in Calais, and the French authorities feel like they are having to deal with Britain’s problem.

“We can’t tolerate what is going on in Calais – the image is disastrous for our country and there are also extremely serious economic and security consequences for the people of Calais,” Juppé said in Paris.

“So the first thing is to denounce the Le Touquet accords. We cannot accept making the selection on French territory of people that Britain does or doesn’t want. It’s up to Britain to do that job.”

Asked specifically if he thought the border should be pushed back to the English coast, he replied: “Of course. Don’t tell me that it’s difficult because the British don’t want it.”

A Downing Street source said: “This is a longstanding bilateral agreement that works for both sides. We would expect to see it continue.”

May was optimistic at the end of her first summit dinner, telling reporters: “It’s about seizing the opportunities of Brexit and forging an ambitious and optimistic new role for Britain in the world.”

She added: “Yes, the UK will be a fully independent sovereign country, free to make our own decisions on a whole host of issues, such as how we choose to control immigration, but we still want to trade freely in goods and services with Europe,”

But that dinner lasted six hours, with May given five minutes at around 1am.

Discussions centred on Russia, Syria and migration. As May spoke, most of the EU leaders were silent. Some started putting their jackets on, waiting for her to finish.

Both Hollande, who is also running for French President, and German Chancellor Angela Merkel have warned May that “hard Brexit”, effectively leaving the single market and opting out of the free movement of people, would lead to tough negotiations.

EU officials are now preparing for the possibility of dirty Brexit, where no deal is reached and the UK just leaves at the end of the two-year negotiation process.

Perhaps most dishearteningly for Brexit negotiators was the news that a major trade agreement between Canada and the EU was on the brink of collapse. Canadians walked out of talks on Friday, after a tiny region in Belgium vetoed the deal that has been seven years in the making.

Wallonia, population 3.5 million, is blocking the trade deal, as in Belgium all major international deals need to be signed off by regional parliaments.

Wallonian farmers are opposed to the deal because they fear the country will be flooded with cheap agricultural imports.

Chrystia Freeland, Canada’s international trade minister, said: “It’s become evident for me, for Canada, that the European Union isn’t capable now to have an international treaty even with a country that has very European values like Canada. And even with a country so nice, with a lot of patience like Canada.”