France on Tuesday warned that it could cut the power supply of the British crown dependencies of the Channel Islands to put pressure on London over fishing rights.
Britain has refused to grant all the fishing licences sought by French boats as part of a post-Brexit access deal, leaving Paris furious and fishermen worried for their livelihoods.
France "will not stand for this", European Affairs Minister Clement Beaune told the Europe 1 broadcaster.
"For example, you could imagine the Channel Islands, where the United Kingdom depends on us for its energy supply...," Beaune said.
He did not expand further, but the warning echoes an earlier threat by Fisheries Minister Annick Girardin who said in May that the fishing row could have an impact on "the power supply by undersea cable" from France to Jersey.
Channel Islands Jersey and Guernsey are close to France which supplies them with electricity.
France said last week that it would quickly lay out retaliatory measures over fishing rights "towards the British and also our neighbours in Jersey".
Fishing rights for EU boats in UK waters were a key stumbling block to negotiations for a post-Brexit trade accord between London and Brussels after Britain's exit from the bloc on January 1, 2021.
The dispute flared in May when a flotilla of around 50 French trawlers massed in front of the Saint Helier harbour on Jersey, a self-governing territory that along with fellow crown dependency Guernsey depends on Britain for its defence.
The protest sparked a tense standoff that even drew in French and British military vessels.
Since then, French fishermen have applied for the new access licences but complain of onerous paperwork and a requirement to prove they had fished in British and Jersey waters before Brexit, not always an easy task, especially for smaller boats.
Last week, Britain said it would grant just 12 out of 47 applications for new licences for small EU boats, while Jersey issued 64 full and 31 temporary licences but refused 75 applications.
"Our patience has clear limits," Beaune said. "We've negotiated calmly and nicely for nine months now, that's enough."
Referring to the UK government, the minister added: "They think they can live all by themselves and, what's more, lash out at Europe. And because that's not working they raise the stakes and become aggressive."
Last week, Girardin said London may be playing hardball on fishing in order to press its demands on other thorny post-Brexit discussions such as migrants seeking to cross the Channel.