France is reportedly set to demand hundreds of millions of euros from Britain to pay for new customs controls at Calais and its other Channel ports post Brexit.
The UK currently contributes to managing its border check points on France's mainland under a deal known as the Le Touquet Treaty.
But the cost of beefing up existing controls after Britain leaves the EU is expected to mushroom.
According to several British media reports, most notably in the Daily Telegraph, President Emmanuel Macron is facing pressure from French politicians to raise the issue with Prime Minister Theresa May at an Anglo-French summit in London next month.
Leading Brexiteers, however, have also chipped in, insisting the UK must not pay any more than it has already agreed with Brussels under the so called Brexit divorce bill.