PARIS ― The European Commission is to assess the “one in, one out” agreement between France and the United Kingdom meant to curb illegal migration, it said Friday.

“The rising number of migrants smuggled across the Channel is alarming and it merits a robust response to deter dangerous journeys at one of the Union’s external borders,” Markus Lammert, Commission spokesperson said, underlining that the EU’s support goes to “solutions that are compatible with the spirit and the letter of EU law.”

The accord, which French President Emmanuel Macron and British Prime Minister Keir Starmer unveiled on Thursday, allows the U.K. return migrants to France who have illegally crossed the English Channel. Because the EU has responsibility for migration issues rather than national governments it will have to approve the deal on France’s behalf.

A French official briefed on the negotiations, granted anonymity to discuss the status of ongoing talks, said Paris had been in contact with Brussels about the legal approval of the deal before it was publicly announced and was hoping for a swift and positive outcome.

In exchange for each migrant returned to France, Paris will transfer one asylum seeker to the U.K. ― generally someone with a family connection or other reason to seek sanctuary there.

French border forces will also be able to take proactive measures to stop boats in shallow waters, subject to a review by the French maritime authorities.

‘Humiliation’

Starmer is under pressure to reduce levels of illegal migration as a record 21,000 people have arrived in the U.K. via the English Channel so far this year. Channel crossings have also proven to be a major political vulnerability for the Labour government as Nigel Farage’s populist Reform UK party continues to climb in the polls.

Farage branded the deal a “humiliation” after it was announced.

Humanitarian organizations believe the agreement is a step in the wrong direction.

“It is absurd to consider sending people back to France when that is the country they decided to leave,” Doctors Without Borders said in a statement.

Michaël Neuman, the head of the organization’s migration unit, said that the British need to stop “outsourcing” border controls to France.

Victor Goury-Laffont reported from Paris and Ferdinand Knapp from Brussels. Esther Webber and Clea Caulcutt contributed reporting from Northwood, England.