Sebastien Pive, Dunkirk’s public prosecutor, announced a manslaughter inquiry, saying the boat had been so overloaded it broke down and sank.

It is the second Channel tragedy in just over a week, after three Somali migrants were lost at sea from a dinghy that was finally picked up 30 miles off Harwich, in Essex. Two other Somalis were rescued from the boat.

Record number of Channel migrants reach UK

A further 500 migrants are thought to have reached the UK on Wednesday in small boats from France, after Tuesday saw 456 people cross in 15 boats.

That takes the total for the year to date past 20,000 for the first time, more than double the 8,417 crossings in the whole of 2020.

It came as it emerged Priti Patel has paid France the first instalment of the £54 million to counter Channel migrants, after the French promised to intercept 100 per cent of the boats.

The Home Secretary agreed to release the cash after her French counterpart, Gerald Darmanin, confirmed his maritime and police forces could stop all the migrants if the UK paid the full amount.

The money is being used by the French to maintain a doubling of police beach patrols, as well as additional technology to spot them, and new reception centres away from the coast.

The French have so far managed to intercept fewer than half of the migrants.

A government source said the Home Secretary only agreed to the money after Mr Darmanin’s pledge. 

“He thinks it’s doable. So we will want to see that. I think they know they need to act,” the source said.

The Home Office has confirmed that not one of the 20,700 migrants who have reached the UK this year has been returned to the EU countries through which they passed, where they should have claimed asylum instead of the UK.

A government source claimed the EU was “dragging its feet” in negotiating a new deal to take back migrants who had passed through “safe” third countries.