PARIS — French authorities said Thursday that they had detained a British fishing trawler, prompting the government in London to summon France’s ambassador for talks, escalating months of rising tension between the two nations.
The confrontation was the latest in a series of cross-Channel flare-ups over post-Brexit fishing rights that have led to accusations of bad faith, threats and even a brief naval standoff in May between the two NATO allies.
Thursday’s moves will likely stoke tensions in French-British affairs that have become increasingly frayed as both nations have tried to define a new relationship after Britain’s departure last year from the European Union.
French leaders were infuriated in September when the United States and Britain announced a deal to develop nuclear-powered submarines for Australia, prompting Australia to cancel a French contract to build conventional submarines. The episode played into longstanding French concerns about the English-speaking nations looking out for their own interests, without regard for their European allies.
But the most persistent irritant between the two neighbors has been a dispute over fishing rights that has ballooned into a diplomatic feud around how to implement a post-Brexit agreement — an issue that both French and British officials hoped they had put behind them.
The agreement, struck in December, provides that European fishermen can keep working in some British waters if they can prove that they were fishing there before Brexit. But French and British authorities have been arguing over the nature and extent of the documentation required, and Britain has refused permission to dozens of French boats.
After weeks of warning that it would take retaliatory measures, a French patrol vessel, checking on fishing vessels near the port of Le Havre on Wednesday night, fined two British trawlers, and detained one of them at the port because it did not have a license to operate in French waters, the maritime ministry said.
The ministry said the detained vessel, the Cornelis Gert Jan, could have its catch seized and could be held pending payment of a monetary penalty, and its captain could be subject to additional punishment.
A day earlier, French authorities had said that if the situation did not improve by Nov. 2, France would close most of its ports to British fishing boats and would increase customs and health checks on goods crossing the Channel. They added that further measures could be considered, including reviewing energy supplies to Britain.
“Now, we have to speak the language of force, because, unfortunately, this British government only understands that,” Clément Beaune, France’s minister for European affairs, told CNews TV on Thursday.
Britain’s foreign secretary, Liz Truss, tweeted, “I have instructed Europe Minister Wendy Morton to summon the French Ambassador to the UK for talks tomorrow to explain the disappointing and disproportionate threats made against the UK and Channel Islands.”
David Frost, Britain’s Brexit secretary, wrote on Twitter that his country had “granted 98 percent of license applications from EU vessels to fish in our waters.”
But on Thursday, Annick Girardin, France’s maritime minister, said the true figure was 90 percent, and that almost all of the boats that have not received British licenses were French.
Fishing was one of the thorniest issues when Britain negotiated its new trade agreement with the European Union, which took effect in January. It ended decades during which Britain’s fishing fleet was under the same E.U. system as France’s, with their catches negotiated regularly among the member countries — though even then, they clashed over whether the rules were fair, or were being followed.
“This isn’t a war, but it’s a fight,” Ms. Girardin told RTL radio on Thursday. “French fishermen have rights, a deal was signed and we must implement this deal.”