“It is Europe’s deepest values – humanism, respect for the dignity of each person – that are in mourning,” Macron said.

Prime Minister Jean Castex will hold a crisis meeting on Thursday with ministers to discuss new measures, his office said.

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, according to public prosecutors in Lille. A manslaughter probe has been opened.

The disaster also poses a new challenge to cooperation between France and Britain after Brexit. Tensions had already been growing over the record numbers of people crossing, adding to a litany of problems that also include fishing rights.

Interior Minister Gerald Darmanin said a total of five suspected traffickers accused of being directly linked to the doomed crossing had been arrested, the fifth man suspected of buying inflatable boats for the crossing.

Darmanin said that only two survivors, an Iraqi and Somali, had been found and they were recovering from extreme hypothermia and would eventually be questioned.

Calais mayor Natacha Bouchart said a pregnant woman was also one of the victims.

UK stokes tensions with France over plans to turn away migrant boats

French officials said earlier three helicopters and three boats had searched the area, finding corpses and people unconscious in the water, after a fisherman sounded the alarm.

Johnson said he was “shocked, appalled and deeply saddened by the loss of life at sea”, following a crisis meeting with senior officials.

But he also said Britain had faced “difficulties persuading some of our partners, particularly the French, to do things in a way that the situation deserves”.

“The response must obviously also come from Britain,” said Darmanin, calling for “a very tough coordinated international response”.

In telephone talks, Johnson and Macron agreed on the “urgency of stepping up joint efforts to prevent these deadly crossings” and that “it is vital to keep all options on the table” to break the business model of the smuggling gangs, according to Downing Street.

British media reports said the UK government is keen to revive an idea for joint British-French patrols on the coast of northern France which has in the past been rejected by Paris.

One of the French lifeboat workers, Charles Devos, described seeing “a flat, deflated inflatable boat with the little air that remained helping it float” surrounded by bodies of the drowned.

Britain and France again clash over post-Brexit fishing row

Pierre Roques of the Auberge des Migrants NGO in Calais said the Channel risked becoming as deadly as the Mediterranean, which has seen a much higher toll from migrant crossings.

“People are dying in the Channel, which is becoming a cemetery. And as England is right opposite, people will continue to cross,” he said.

According to the French authorities, 31,500 people attempted to leave for Britain since the start of the year and 7,800 people have been rescued at sea, figures which doubled since August.

In Britain, Johnson’s Conservative government is coming under intense pressure, including from its own supporters, to reduce the numbers.

Darmanin said France had arrested 1,500 people smugglers since the start of the year.

He said they “operate like mafia organisations”, using encryption to stop police tapping their phone conversations.

Natalie Elphicke, Conservative MP for the Channel port of Dover, called the sinking “an absolute tragedy” and demonstrated the need to stop the crossings at their source.

Charlotte Kwantes of Utopia56, an association that works with migrants in Calais, said “more than 300” migrants had died since 1999 in the area.

“As long as safe passages are not put in place between England and France, or as long as these people cannot be regularised in France … there will be deaths at the border,” she said.

According to British authorities, more than 25,000 people have arrived illegally so far this year, already triple the figure recorded in 2020.