PARIS — French officials lashed out at Britain on Friday over a letter from Prime Minister Boris Johnson advising France to take back migrants who reach British shores, escalating a diplomatic spat just days after 27 people died trying to cross the English Channel.
The French denounced Mr. Johnson’s statement in blunt terms, calling it unacceptable, and disinvited Britain’s home secretary, Priti Patel, from a crucial meeting on the migrant crisis on Sunday.
The dispute, in the immediate aftermath of one of the deadliest disasters ever in the English Channel, underscored the diplomatic hurdles the two countries face in addressing the problem, as lingering tension over Brexit and disagreements on issues including trade and fishing rights continue to roil their relationship.
In a letter sent to President Emmanuel Macron of France on Thursday night, Mr. Johnson wrote that France and Britain should “put in place a bilateral readmissions agreement to allow all illegal migrants who cross the Channel to be returned,” suggesting that if France took back migrants it would be a major step toward fixing the problem.
The letter prompted a fierce reaction from Gabriel Attal, a French government spokesman, who said the letter was “both poor in content and completely inappropriate in its form.”
“Enough with the doublespeak, enough with the constant externalization of problems,” Mr. Attal, visibly irritated, told BFMTV on Friday morning. “It makes you wonder if Boris Johnson doesn’t regret having left Europe, because every time he has a problem, he thinks that Europe should handle it.”
Gérald Darmanin, France’s interior minister, quickly announced that Ms. Patel was no longer invited to an emergency meeting that France will hold in Calais on Sunday with ministers in charge of immigration from neighboring countries like Belgium and Germany.
Mr. Macron said on Friday that the crisis required “serious” cooperation — but that Mr. Johnson’s letter was not a serious effort.
“You don’t communicate from one leader to another on these issues by tweets and by letters that you make public, we aren’t whistleblowers, come on,” Mr. Macron said at a news conference in Rome, where he was on an official visit.
On Wednesday, about 30 migrants crammed onto a flimsy inflatable vessel were shipwrecked in the English Channel’s frigid waters, and most of them — men, women and children — drowned. French prosecutors have opened an investigation to determine the exact circumstances of the disaster, and the identities and nationalities of most of the victims have not been confirmed.
The number of migrants setting off into the sea has soared in recent months because France has cracked down on other routes to England, especially by ferry or by truck and train through the tunnel under the Channel. So far this year, there have been 47,000 attempts to cross the Channel, and 7,800 migrants had been saved from shipwrecks, according to French officials.
On Twitter, where he also published the full letter to Mr. Macron, Mr. Johnson wrote that “an agreement with France to take back migrants who cross the Channel through this dangerous route would have an immediate and significant impact.”
“If those who reach this country were swiftly returned, the incentive for people to put their lives in the hands of traffickers would be significantly reduced,” Mr. Johnson said. He called it “the single biggest step” the two countries could take to address the issue.
In his letter, Mr. Johnson noted that countries like Russia and Belarus already have readmission agreements with the European Union and that any bilateral agreement between France and Britain would be temporary, pending a broader deal between the E.U. and Britain.
He also outlined other proposals, including better intelligence sharing, joint police patrols on French shores — which France has already rejected — and reciprocal maritime patrols in each country’s territorial waters.
But French officials reacted furiously on Friday morning to the suggestion that France should take back migrants, calling the idea a nonstarter and accusing Mr. Johnson of using the migration crisis for domestic political ends.
Mr. Darmanin, in a letter sent to Ms. Patel and that was seen by the Agence-France Presse, said he was “disappointed” by the demands made in Mr. Johnson’s letter and found it “even worse” that he had made them public.
Mr. Attal, the French government spokesman, told BFMTV that the publicly shared letter “did not match, at all, the exchanges that Boris Johnson had with the President over the phone as recently as Wednesday evening.”
Mr. Attal added that the suggestion France should take back migrants who reach British shores “is obviously not what we need to fix the problem.” Instead, he said, Britain should send its own immigration officials to France, where they would examine the claims of asylum seekers trying to reach British shores.
Grant Shapps, the British Transport secretary, defended Mr. Johnson’s letter, telling the BBC that “friends and neighbors” had to work together and that he hoped France would reconsider disinviting Ms. Patel.
“It’s in our interests,” he said. “It’s in their interests. It’s certainly in the interests of people who are being people-trafficked to the U.K, with these tragic scenes we’re seeing.”