British Prime Minister Boris Johnson wrote to French President Emmanuel Macron on Thursday asking France to immediately start taking back all migrants who land in England after crossing the Channel, after at least 27 died when their boat foundered off Calais.

Taking back migrants "would significantly reduce – if not stop – the crossings, saving thousands of lives by fundamentally breaking the business model of the criminal gangs" behind the trafficking, he said in a letter sent to Macron on Thursday evening.

Johnson's letter also set out areas for greater cooperation with France, proposing joint border patrols, aerial surveillance and intelligence sharing.

"We are ready to begin such patrols from the start of next week," Johnson said.

Britain and France had earlier called for a coordinated European response to stop people-trafficking in the Channel after the deadliest accident since the waterway in 2018 became a key route for migrants from Africa, the Middle East and Asia trying to reach England from France.

Home Secretary Priti Patel spoke with French counterpart Gerald Darmanin to put forward plans for greater "collaboration and innovation," according to a statement.

It said the two will meet this weekend, and Patel will send officers to Paris after having offered to provide more people on the ground.

Macron, after vowing France would not allow the Channel to become a "cemetery," spoke earlier to Johnson to agree on stepping up efforts to thwart the traffickers blamed for the surge in crossings.

The Elysee Palace said Macron told Johnson that France and the UK have a "shared responsibility" and added he "expected the British to cooperate fully and refrain from exploiting a dramatic situation for political ends."

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"France is a transit country, we are fighting against these networks of smugglers who exploit people's misery, but for this we must improve European cooperation," Macron said on a visit to Croatia, saying that when the migrants arrived in northern France "it is already too late."

Seventeen men, seven women and three minors died when the inflatable boat lost air and took on water off the northern port of Calais on Wednesday. A manslaughter probe has been opened.

More than 25,700 people have made the cross-Channel journey in small boats this year – three times the total for the whole of 2020, according to data compiled by Britain's PA news agency.

French Prime Minister Jean Castex held a crisis meeting on Thursday with ministers to discuss new measures and invited the British, Belgian Dutch and German immigration ministers to a meeting in Calais next Monday.

(With input from AFP)