Fishing rights for EU boats in UK waters was a key stumbling block to negotiations for a Brexit trade accord between London and Brussels, and threatened to sink the deal.
But the issue has resurfaced after Britain on Tuesday said it would grant just 12 out of 47 applications for new licences for small EU boats to fish in its territorial waters.
On Wednesday, the self-governing British Crown dependency of Jersey refused 75 applications from French boats, and issued 31 temporary licences: 75 bids were accepted.
French government spokesman Gabriel Attal said the decisions were “totally unacceptable and inadmissible” and “contravene the agreement that was signed in the framework of Brexit”, threatening retaliation via Brussels.
“We are going to continue and step up our work with the (European) Commission to move forward on this issue, and also to study possible retaliation measures that could be taken if the agreement is not respected,” he added.
UK-French relations are already strained, with Paris accusing London of going behind its back to sign a new defence deal to provide US-built nuclear-powered submarines to Australia.
Dimitri Rogoff, president of the regional fisheries committee in Normandy, told AFP that fishermen were preparing to protest.
“They are ready to attack (Jersey’s capital) Saint Helier. It is tense, very very tense,” he added.
Olivier Lepretre, president of the regional fisheries committee in the northern Hauts-de-France region, added: “There comes a time when we must put pressure on the British side.”
He suggested the fishermen had the “port of Calais in their sights”, raising the possibility of a blockade on the key gateway for goods travelling from mainland Europe to Britain.
In Jersey, which sets the terms of fishing in its waters under the Brexit deal agreed last year, all unlicensed boats must stop fishing in its waters within 30 days, although it will still accept and consider new evidence to support bids.
“By issuing these licences in the days ahead, we are ensuring the fishing effort in our waters is similar to pre-Brexit,” said the Channel island’s Environment Minister John Young.
“Those boats with an economic dependence on Jersey waters, who’ve fished here regularly before and have demonstrated it, will receive licences.”
In refusing licenses on Tuesday, the UK government insisted it had pursued a “reasonable approach”, issuing a total of nearly 1,700 licences to boats from the bloc to fish in Britain’s exclusive economic zone, which is defined as being 12-200 nautical miles from the coast.
But French Maritime Minister Annick Girardin called it “a new British refusal to apply the conditions” of the Brexit agreement struck by London and Brussels.
Stormy protests by French trawlers over fishing rights in Jersey erupted earlier this year and even threatened to turn into a full-blown naval incident.
As French trawlers steamed towards the capital Saint Helier, London sent two naval patrol boats to monitor the situation, prompting Paris to respond in kind.
In a bid to calm tempers, a three-month extension was agreed for EU boats to fish in Jersey waters. That expires this week, although vessels will still be able to operate for the next month.
Neighbouring Guernsey, which also implements fishing rules in its waters, on Wednesday announced a “roadmap” to issuing licences to French vessels, with the grace period extended until January while the decisions are made.
Before Britain left the bloc, boats from EU countries were allowed to fish in British waters subject to agreed quotas on what they could catch.