Five other people were recovered in "serious condition" and taken to a hospital in Calais by helicopter and 50 people have been rescued, French authorities said.

A search and rescue operation involving five French ships, two British ships and a helicopter is under way following the incident off Cap Gris Nez in northern France.

Local mayor Franck Dhersin said a vast rescue operation was launched at around 4am UK time, as dozens of boats tried to make the crossing at the same time.

He said: "Near Sangatte they unfortunately found dead people".

A UK government spokesperson says it is "aware of the incident in the Channel", adding: "HM Coastguard are working on a coordinated response and further information will be provided in due course."

France's Maritime Prefecture of the Channel and the North Sea said "at this stage about fifty people have been rescued, some of them by British means.

"Unfortunately, six people were recovered in serious condition and one of them, evacuated by helicopter to Calais hospital was declared dead."

Read more:
More than 100,00 people have crossed Channel in small boats
Tory MP's 'f*** off back to France' comment shows govt trying to distract from failings

HM Coastguard said it is assisting French authorities in response to the incident involving a "small boat", adding that a Dover RNLI lifeboat has been sent as part of that assistance with Folkestone and Langdon Bay coastguard rescue teams.

The UK coastguard is also working with the South East Coast Ambulance Service.

The number of people who have crossed the English Channel in small boats in the past five years has passed 100,000.

Click to subscribe to the Sky News Daily wherever you get your podcasts

The latest Home Office figures show 755 migrants were detected in the Channel on Thursday, the highest daily figure so far this year.

The Channel is one of the world's busiest shipping lanes and currents are strong.