The French Navy allowed a dinghy packed with migrants to continue across the Channel to Britain despite the deaths of five people, including a seven-year-old girl, on board.
Three men and a woman died alongside the girl, who was crushed when people smugglers crammed more than 100 migrants onto the dinghy.
It crossed the Channel after setting off from Plage des Allemands beach in Wimereux, near Bologne, northern France.
Some 49 of the 112 migrants on the dinghy were brought back to shore or taken to Boulogne after being rescued.
However, 58 people remained on the small boat after refusing to be rescued and were allowed to continue their journey to Britain, escorted by a French navy ship. One of the women brought to shore in the UK had a broken leg.
The five were pronounced dead despite attempts to resuscitate them after they were brought to the beach. French officials said they had never experienced so many migrants being packed onto a single boat.
The deaths came hours after Parliament finally passed Rishi Sunak’s Safety of Rwanda Bill into law, paving the way for the first deportation flights aimed at deterring the Channel crossings.
The Prime Minister said criminal gangs were exploiting the vulnerable and “packing more and more people into these unseaworthy dinghies”. Speaking during a flight to Poland, he said the tragedy “underscores why you need a deterrent”.
“This is what tragically happens when they push people out to sea and that’s why, for matters of compassion more than anything else, we must actually break this business model and end this unfairness of people coming to our country illegally,” he said.
On Monday, Home Office figures showed that the number of migrants arriving by small boats across the Channel had increased by 24 per cent to 6,265 in the first four months of this year, compared with 5,049 last year.
Andrew Harding, a BBC reporter, witnessed the migrants charging from sand dunes to reach the boat, with several of the men brandishing long sticks and throwing flares or firecrackers. Two women and a child who could not keep up were stopped by police.
He said: “Once the migrants had boarded the inflatable boat they’d been dragging across the sand, the police made no further attempt to stop them.”
The Maritime prefecture said the victims had been crushed under the weight of migrants desperate to board the dinghy.
The seven-year-old girl’s father saw her die, according to charity workers who found him on the beach at Wimereux. “He was in tears. We know him well because we often see him here,” an aid worker told La Voix du Nord, a local newspaper. “These are people who have tried to cross several times.”
Jacques Billant, the prefect of Pas-de-Calais, said the 112 people who were crammed on board was unprecedented. The numbers being carried on dinghies have doubled in the past two years to average between 50 and 60.
“This has never been seen before,” said Mr Billant. “A few hundred metres from the coast, the engine stopped and several people fell into the water.”
A patrol boat sent to rescue the migrants had found several people unconscious, he added.
The remaining 58 people on the boat continued their journey, and Mr Billant said: “They managed to restart the engine and decided to continue their sea route towards Great Britain under the surveillance of course of the French navy.”
Under the French interpretation of maritime law, the French navy will not intervene to stop or turn back migrants at sea unless they request assistance because of the risk to life.
Although the weather was calm on Tuesday morning, conditions remained difficult, with an air temperature of zero degrees Celsius early on Tuesday morning and a water temperature of no more than 10C.
Several dozen boats carrying migrants are reported to have left beaches around Calais at 3am as people smugglers exploited the favourable weather conditions and relatively calm sea.
During the night, French police officers had intercepted two boats, two fuel cans, two engines and life jackets before they could be used to put migrants to sea.
James Cleverly, the Home Secretary, said: “These tragedies have to stop. I will not accept a status quo which costs so many lives.
“This Government is doing everything we can to end this trade, stop the boats and ultimately break the business model of the evil people smuggling gangs so they no longer put lives at risk.”
Enver Solomon, the chief executive of the Refugee Council, said: “This is another devastating human tragedy that could and should have been avoided – and for it to happen just hours after the Government’s Rwanda Bill became law makes it all the more tragic.
“The only sustainable way to reduce dangerous journeys across the world’s busiest shipping lane is for the Government to reduce the need for desperate people to take desperate actions.
“Instead of hostile, headline-grabbing legislation, we need to see safe routes for those fleeing conflict and persecution, including more options for family reunion, refugee visas, and cooperation with our European neighbours.
“We don’t need costly and unworkable laws – we need a fair and humane process that upholds the right to asylum, ensuring refugees are treated with dignity and respect.”
The incident comes six weeks after a seven-year-old girl drowned in the Aa canal at Watten, which flows into the North Sea, while in a small boat with 15 other migrants.
At the end of February, a 22-year-old Turkish man died when he fell from his boat off the coast of Calais. An Eritrean was indicted and detained on Saturday in connection with the case.
On the night of Jan 13, five migrants, including a 14-year-old Syrian teenager, died at Wimereux as they tried to reach a boat already at sea in 9C water.