The mayor of the northern French city of Calais has threatened to block the port unless Britain does more to control the number of illegal migrants, reports the BBC.
Natacha Bouchart said that her city was being "taken hostage" by about 1,300 migrants from the Middle East, Asia and Africa who are attempting to cross the English channel from France.
She said that the migrants were costing too much and making life unpleasant.
Many believe the UK will be a more welcoming place if they can get there.
In 2002 the French government closed the main Red Cross centre at Sangatte near Calais, but unsanitary illegal camps have constantly sprung up in its place since then.In recent months French police have tried to break up the camps, but the migrants say they have nowhere else to go. They can be seen sheltering under plastic bags and sheets, and many depend on charities for food.
"I could take the decision to block the port. I could bring pressure to bear," Ms Bouchart told journalists in Paris after discussing the problem with interior minister Bernard Cazeneuve.
"It would be illegal," she accepted, "but today I want to make a strong gesture towards the British."
The mayor complained that British immigration policy made the UK be seen as "an Eldorado" by immigrants.
Read more of this report from the BBC.