“We are ready to use these retaliation measures,” Maritime Minister Annick Girardin told lawmakers in parliament

She mentioned in particular consequences involving the underwater cables that supply electricity from France to Jersey, the largest Channel island.

“I am sorry it has come to this,” Girardin said, but “we will do so if we have to.”

Paris and London have increasingly clashed over fishing in recent weeks, as French fishermen say they are being prevented from operating in British waters because of difficulties in obtaining licences.

In the latest move, Britain on Friday authorised 41 ships equipped with Vessel Monitoring System (VMS) technology — which allows ships to be located — to fish in waters off Jersey, a self-governing British Crown Dependency.

But this list was accompanied by new demands “which were not arranged or discussed (with France), and which we were not notified about”, the French fisheries ministry said.

The measures effectively create new zoning rules for the waters near Jersey — “where the ships can go and cannot go”, as well as the number of days the fishermen can spend at sea and using what machinery, the ministry added.

“This is absolutely unacceptable,” Girardin said. “If we accept this for Jersey, it would imperil our access everywhere.”

France and Britain have increasingly clashed over fishing in recent weeks, with French fishermen saying they are being prevented from operating in British waters because of difficulties in obtaining licences.

The French fisheries ministry said Britain had introduced “new technical measures” relating to licences for fishing off the Channel Islands which had not been properly declared to the European Union under the terms of the Brexit deal.

“We consider that if the new demands for sea zoning or fishing equipment are integrated into the licences – when the European Commission has not been notified – they are null and void,” the ministry told AFP.

The ministry said it was adhering “strictly to the deal” agreed on fishing under the terms of Britain’s exit from the European Union on January 1st.

“If the United Kingdom wants to introduce new measures, it must notify the European Commission which in turn notifies us – that allows for us to engage in a dialogue,” the ministry said.

“These new technical measures are not applicable to our fishermen as things stand.”

READ ALSO: France warns UK: ‘Our fishermen are as important as yours’

Fishing proved one of the most fraught issues in the frantic negotiations leading up to Britain’s departure from the EU, with London tightly guarding control over its waters as a symbol of its sovereignty.

Reprisal measures?

France said it had voiced its displeasure at the surprise measures with the European Commission.

Commission spokeswoman Vivian Loonela said the EU was engaged in “intense joint work” with the British government to resolve the issue.

“Any condition should be notified in a timely way to allow the other party sufficient time to comment or adapt,” she said of the new British requirements.

“In addition, any such conditions cannot be discriminatory towards our fishermen.”

Dimitri Rogoff, president of the regional fishing committee of Normandy in northern France, said that if French fishermen continued to be blocked from the waters off Jersey, there should be reprisal measures.

“Fishermen from Jersey should not be able to land at Granville,” he said, referring to the French port nearest the island.

French fishermen last month began a protest movement, blockading trucks bringing fish from Britain to France, over complaints that few of their vessels have obtained licences to operate in British waters.