A total of 973 migrants in 17 boats crossed the English Channel on Saturday – the highest daily number this year.
The figure beats the previous record for 2024 – which was 882 people on 18 June.
It comes as French authorities said four people died while attempting to cross the Channel on Saturday – including a two-year-old boy who was “trampled to death”.
Jacques Billant, prefect of Pas-de-Calais region, said the French coastguard had responded to a boat carrying almost 90 people which suffered engine failure.
Fifteen people were transferred to a tow vessel, including the boy, who was unconscious.
A medical team was sent by helicopter, but he was pronounced dead.
He was “trampled to death”, French interior minister Bruno Retailleau said on X.
He added: “The people smugglers have the blood of these people on their hands and our government will intensify the fight against these mafias who are getting rich by organising these crossings of death.”
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Yvette Cooper, the UK home secretary, replied to Mr Retailleau on the social media site, saying it was “appalling” that more lives had been lost in the channel, “including a young child”.
“Criminal smuggler gangs” do not care “if people live or die”, she added.
In a second incident, a boat with 83 people on board also suffered engine failure.
Three passengers – two men and a woman – were found unconscious at the bottom of the vessel, Mr Billant said. They were “probably crushed and suffocated”.
The total number of deaths so far this year is 51, Mr Billant told reporters. The figure for 2023 is reportedly 12.
The migrants rescued on Saturday were from Eritrea, Vietnam, Afghanistan, Iran, Ethiopia, Libya, Syria, Egypt, Kuwait and Iraq, he added.
This week, the UK and other G7 nations agreed an anti-smuggling action plan designed to boost co-operation.
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