French plans to intercept people smugglers guiding small boats at sea – so-called “taxi boats” – could be blocked by legal action.

The charity that successfully helped block Dame Priti Patel’s plans to turn back migrant boats in the Channel has said it is ready to support any migrants or organisations seeking to mount a court challenge.

Care4Calais, which also launched the first legal challenge to the Tories’ Rwanda deportation plan, said it had not ruled out mounting a court action itself against the “dangerous” tactics.

The move comes as France prepares to start intercepting migrant “taxi boats” at sea for the first time.

The tactics have yet to be finalised but are expected to see border police, gendarmes and coastguard vessels stop boats from leaving waters within 300 metres of the coastline.

It is thought they will aim to intercept the “taxi boats” packed with migrants not only in shallow waters as they leave the beaches but also when they make their way from rivers and inland waterways, often miles away, to pick up the asylum seekers.