The frontrunner in the French presidential race has said he would tear up a treaty allowing UK border officials to carry out migration checks in Calais.
Alain Juppe, who is bookies' favourite to succeed Francois Hollande in next year's election, said the border should be pushed back to the British side of the Channel where the UK should deal with migrants seeking to enter the country.
He blamed the 2003 Le Touquet agreement, which allows British officials to check passports on French soil, for the creation of the makeshift "Jungle" encampment in Calais, where thousands of would-be migrants await their chance to cross to the UK.
Speaking to a group of European newspapers including The Guardian, Mr Juppe said: "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.
"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 whether the Anglo-French border should be pushed back to the Kent coast, he said: "Of course. Don't tell me that it's difficult because the British don't want it.
"If we entered international negotiations in that spirit, there would never be any negotiations. So the debate must be opened and a new accord obtained with Britain."
The right-of-centre former French prime minister said he "respected" the result of Britain's referendum decision to leave the EU, adding: "Now it must be put into action quickly."
Britain cannot be both "outside and inside" the EU, but France will want to keep "very close bilateral cooperation with the UK" after Brexit, particularly on military and defence issues, he said.
Dover MP Charlie Elphicke said: "Dumping the Calais border controls is a crackpot idea. Making it easier to break into Britain would just turn Calais into an even bigger magnet for migrants.
"We need less bluster and more border security. There wouldn't be any migrants at Calais if they had no hope of getting through.
"That's why Britain and France must work together to help the vulnerable, make our borders stronger and wage war on the people traffickers who are behind this crisis to end their evil trade of modern slavery once and for all."
A Downing Street spokesman said: "The Home Secretary has had two meetings now with her French counterpart at which this issue has been discussed, and it's been made perfectly clear that both the French government and the British Government are committed to the Le Touquet agreement. Nothing has changed and there is no plan at all for it to be torn up."
Asked whether Theresa May was concerned that this position might change after the presidential elections in May next year, the spokesman said: "That's something that will happen in the future. The current French government is clearly of the same view as the British Government that the Le Touquet agreement is working and there are no plans to alter it."