French police said they arrested five gang members on a rented yacht which was being used to transport seven Ukrainian migrants hoping to enter the UK. The Ukrainians had entered France on tourist visas.
Two skippers and three suspected smugglers were detained on Friday in Brittany.
"This migration network used a relatively rare and costly method, because the journey cost around €6,000 to €7,000," said Julien Gentile, head of France's anti-smuggling office.
The authorities believe that over the last two years the gang had rented some 20 boats from different ports along the French coast for their illicit operations.
One of these had been spotted earlier this year and monitored as it passed through Italian, Spanish and British waters before docking at Saint-Quay-Portrieux in Brittany where Friday's arrests occurred.
But the first investigations began in the middle of 2014 when British customs officers discovered six Ukrainians trying illegally to reach shore from a yacht off the eastern coast of England.
