The European Commission said Friday it would examine a deal between Paris and London on returning migrants arriving in the UK, as other EU countries fret over the impact.

Commission spokesman Markus Lammert said the rising number of migrants smuggled across the English Channel was “alarming” and a “robust response” was required to deter the dangerous journeys.

“On the specific envisaged cooperation between France and the United Kingdom, the commission will assess the concrete modalities of this cooperation,” Lammert told reporters in Brussels.

Under the so-called “one in, one out” agreement announced Thursday migrants would be sent back to France in return for the UK accepting a similar number of migrants with strong asylum cases.

The commission has to examine it before it can come into force, and the deal has sparked “serious concerns” among some other European nations.

Their worry is that France would return migrants to the first EU country they arrived in.

More than 21,000 migrants have made the Channel crossing in rudimentary vessels this year alone.