Over 2,300 migrants had to be rescued attempting to cross the English Channel in 2019, four times the number for 2018, local authorities in northern France said on Tuesday.
In total 261 cases of crossings or attempted crossings were recorded by the French and British authorities, mainly in small, often overloaded, inflatable boats, the Maritime Prefecture of the Channel and the North Sea told AFP.
Some 2,358 people had to be rescued compared to 586 in 2018.
Over the past year, growing numbers of migrants from Africa, the Middle East and Central Asia have taken to the treacherous waters of the Channel in small fishing boats or inflatable dinghies.
Rights groups have linked the crossings to a police crackdown to prevent the establishment of migrant camps in Calais and other areas along the French coast.
At least four migrants died in 2019 attempting to make the dangerous crossing in the Channel, one of the world's busiest shipping lanes, with strong currents and icy waters.
A spokesman for the UK's Home Office said a Border Force cutter and two coastal patrol vessels were patrolling the Channel.
"There has also been a doubling of patrols on French beaches and drones, specialist vehicles and detection equipment have been deployed to stop small boats leaving French shores and arriving in the UK illegally.
"Individuals who reach the UK illegally should be in no doubt about our determination to return them to Europe as it is an established principle that those in need of protection should claim asylum in the first safe country they reach."