French President Emmanuel Macron met migrants in the Calais region during a visit on Tuesday

French President Emmanuel Macron and British Prime Minister Theresa May will announce a new treaty on how to handle migrants hoping to head to Britain, the French presidency said Wednesday.

The treaty, set to be announced at a summit in London on Thursday, will "complete the Le Touquet accord", Macron's office said in reference to a 2003 deal that effectively put Britain's border in northern France.

The details are "still being finalised", the French presidency said, but the treaty will include measures on how to manage unaccompanied minors, and Britain will make a "major" financial contribution.

The original text, which came into force in February 2004, implemented joint controls at coastal ports in both countries as Britain, which is not part of Europe's Schengen visa-free zone, looked to bolster efforts to keep migrants out.

Later accords led to Britain financing some of the controls and security operations in Calais, just across the English Channel from its own port in Dover.

Calais has long been a sore point in French-British relations, and Macron on Wednesday called for better cooperation in managing the border with Britain ahead of his first trip to London as president.

- Record asylum claims -

Migrants hoping to stow away on trucks bound for Britain have long been drawn to France's northern coast, with the squalid "Jungle" camp near Calais once housing some 10,000 people before it was bulldozed by the government in late 2016.

Hundreds of migrants remain in the area, with police routinely breaking up makeshift camps of people hoping to head to Britain, a favoured destination for Afghans and east Africans.

French officials argue the Le Touquet deal has worsened Europe's migrant crisis by creating a huge backflow of migrants in the area, lured by a belief that it is easier to secure asylum and work permits in Britain.

A French human rights commission in 2015 said the accord had made France the "police branch" of Britain's immigration policies.

Macron made a renegotiation of the Le Touquet deal one of his campaign pledges, and Interior Minister Gerard Collomb signalled Tuesday that Paris would ask Britain to take in more refugees from northern France and increase its funding.

"It's in their interests that things go well," Collomb said.

In November, Collomb said there were about 300,000 undocumented migrants in France, and the government registered a record 100,000 asylum claims last year.