PARIS — Less than a day after at least 27 migrants died while trying to cross from France to Britain by boat, in the worst migrant tragedy in the English Channel in years, the two countries were sparring Thursday over who was to blame and what should be done in the future.

Britain reiterated calls for joint patrols along the French coast in hopes of preventing migrants from starting the perilous journey across the channel, and France demanded more support from its neighbors. “Yesterday was the moment that many of us have feared for many years,” British Home Secretary Priti ­Patel told Parliament.

In a letter to his French counterpart on Thursday evening, British Prime Minister Boris Johnson called for the establishment of “joint patrols” by Britain and France or by “private security contractors.” Johnson also called for a pact that would allow migrants to be deported back to France.

Previous British proposals of joint patrols had raised concerns in France over sovereignty. The French government accuses Britain of a lack of action against traffickers as well as businesses that employ undocumented migrants. On Thursday, the French called for more European and British support for their efforts to combat human trafficking in the channel.

In a phone call with British Prime Minister Boris Johnson on Wednesday evening, French President Emmanuel Macron “underlined the shared responsibility” and urged Britain to “refrain from exploiting a dramatic situation for political purposes,” the Élysée presidential palace said early Thursday.

Speaking on French radio Thursday morning, French Interior Minister Gérald Darmanin said “pregnant women, children died” in the tragedy in the channel. A local prosecutor told Agence France-Presse that 17 men, seven women and three presumed minors are known to have died. Efforts to identify the victims and their countries of origin were underway.

Two people, from Iraq and Somalia, survived and were treated for hypothermia, according to Darmanin.

In a mayday call obtained by Sky News, the French coast guard can be heard putting out an alert to “all ships” in the area. Charles Devos, a regional manager of the life boat association in Calais, told the broadcaster that when he arrived on the scene, “it was a bit like the film Titanic when you saw all these people plunged into the water, drowning.”

More than two dozen migrants died while trying to reach Britain from France after their boat sank in the English Channel on Nov. 24. (Reuters)

During their call Wednesday, Macron and Johnson agreed to step up Anglo-French cooperation and to do all they could to stop those trafficking migrants, according to Downing Street. But it was also clear that the leaders had different ideas about how to proceed.

French officials have in the past repeatedly accused Britain of responsibility for a surge in migrant crossings in the channel. Darmanin recently singled out British nongovernmental organizations in northern France that “prevent the police and the gendarmerie from working.”

He has also faulted Britain as not acting decisively enough against trafficking networks based in Britain and attracting migrants by allowing “irregular workers” to be “employed at low cost.”

Meanwhile, charities and aid agencies on both sides of the channel have long called on the British government to open safe routes to the country for asylum seekers. Currently, the migrants who are in France can apply for asylum in Britain only if they are physically there — meaning they have to take deadly risks in rickety boats with traffickers.

But speaking to Parliament on Thursday, Patel did not suggest changes to the British immigration system and reiterated an offer to “put more officers on the ground” and “do absolutely whatever is necessary to secure the area so that vulnerable people do not risk their lives by getting into unseaworthy boats.”

She also did not rule out tough new tactics to push boats back toward France.

Speaking to The Washington Post on Thursday, Bruno Bonnell, a French lawmaker for Macron’s party, said joint patrols are “probably a good idea,” partly because they may ease British-French tensions and “finger-pointing.”

But Bonnell said that the patrols should be only the “tip of the iceberg of the solutions” and that an adjustment of immigration policies may be needed on both sides of the English Channel “to help people to legally enter” and “to protect them from the smugglers.”

Nearly three times as many migrants have crossed by sea this year compared with last year as authorities have clamped down on other routes, including crossings by train and cargo trucks. Successful crossings have encouraged a growing number of migrants to attempt the journey via the Dover Strait. But the route, which uses the channel’s narrowest point, also crosses one of the world’s busiest shipping lanes and is highly dangerous for people in small, flimsy boats, especially when strong currents and high winds prevail.

Some policymakers in France dismissed the British proposal for joint patrols. Pierre-Henri Dumont, a lawmaker for Calais, told the BBC that it would not work as there was a “question of sovereignty. I’m not sure the British people would accept it the other way round, with the French army patrolling the British shore.”

He said also that such an undertaking was not practical on the long coastline.

“It only takes 5 to 10 minutes to take a boat and put it at sea filled with migrants, so I’m not sure it is only a question of money and question about the number of [personnel],” he said, echoing reports from French police officers who say they operate under tight rules. French authorities say they are allowed only a limited time window in which to try to prevent crossing attempts — usually after migrants reach the dunes and before the boats are underway.

“If you have the impression that some policemen don’t look at a specific boat, it’s because they usually look at other boats on the other side of the beach,” said Bonnell, the French lawmaker, responding to photos that appeared to show police standing by Wednesday as a group of migrants hurried toward the channel, carrying an inflatable boat.

French police regularly clear makeshift migrant camps on France’s northern coastdrawing complaints of heavy-handedness from migrants and human rights groups. Dumont, the French lawmaker, said one solution was not only to close the migrant camps around the coast, but also to move their occupants into “welcoming centers” where they can apply for asylum in France — or in Britain, where many want to go.

Aid groups say that most migrants who come to Europe remain on the continent, but a minority tries to reach Britain because of family or other ties or because they speak English.

The number of asylum applications to Britain is relatively small in comparison with the numbers received by countries of similar size in Europe. In the third quarter of 2021, 17,400 people applied for asylum in Britain; in France in that same period, 31,000 people applied.

Rob McNeil, a spokesman for the Migration Observatory at the University of Oxford, said that most migrants arriving in Britain on boats are from countries where claims for asylum in Britain are typically approved. Those countries include Eritrea and Syria, where 90 percent of applications are successful as a result of the danger people face in those places, he said.

French officials also called for more support from within the European Union in response to Wednesday’s incident.

In his radio interview Thursday, Darmanin named Belgium, the Netherlands and Germany as countries that are also linked to trafficking networks, adding that one of five people suspected as traffickers involved in Wednesday’s crossing attempt had bought boats in Germany. The five were among more than 1,500 smugglers the French government says it has caught in the region since the beginning of the year.

“We need to stop being effectively the only ones who are able to act against traffickers,” he said.

Wednesday’s tragedy did not deter others from trying to reach England. In the early hours on Thursday, the BBC reported, two boats made the journey across the channel and landed at Dover with about 40 people wearing life jackets and wrapped in blankets.

Adam reported from London.