He says small boats migrants will be returned to France, in exchange for asylum seekers who have not tried to enter the UK illegally.

LONDON—The U.K. and France struck a deal on Thursday to try to slow a record number of migrants crossing the English Channel in flimsy boats, as anti-immigrant populists in both countries lead in the polls.

The UK and France have agreed to a ‘one in, one out’ migrant deal that will see failed asylum seekers returned to France for the first time since Brexit.