Ten European countries have joined France in condemning Britain's approach to post-Brexit fishing access.
In a joint statement the 11 states, including Germany, Italy, Spain, and Belgium, called on the UK to abide by the terms of the Brexit agreement.
The countries are angry that the UK has set high barriers for fishermen to get licences, which they say goes beyond the deal struck between the two countries.
While boats that have historically fished in an area should retain access under the Brexit deal, authorities in Jersey are requiring onerous geolocation data records to prove this.
As a result many French fishermen are effectively being barred from the area.
France has threatened retaliation at a national or European level, including hinting that it could cut off power exports to UK territories.
The statement says the geolocation requirement "is not provided for in the deal, and is not required by European regulations".
It adds: "We therefore call on the United Kingdom to promptly respond and undertake further technical work in accordance with ... the agreement."
The issue is running in parallel to, but separate from, concerns about the Northern Ireland Brexit deal, which is dominating the UK-EU relationship.
French minister Clement Beaune said: “The European Union scrupulously implements the agreement it reached with the United Kingdom. We expect the same from Britain.”
The Brexit deal’s section on fishing disappointed the industry in the UK, which branded it a betrayal and a sell-out.
