THE threat to cut off the UK’s electricity supply if a fishing row is not resolved has been described by Downing Street as “disappointing and disproportionate”.

It comes after a Scottish fishing vessel was detained overnight yesterday amid claims it did not have a proper licence.  

The scallop trawler Cornelis Gert Jan, and its crew, were seized by French authorities yesterday amid a growing row over fishing rights.

The French claim the vessel did not have the correct licences, and it was detained during an operation as “part of the tightening of controls in the Channel, in the context of discussions on licenses with the United Kingdom and the European Commission.”

However the firm which owns the vessel, Macduff Shellfish, said it did have the correct licence and has disputed the French maritime minister Annick Girardin’s claim.

George Eustice, the UK Government’s environment secretary, said the reason for the detention was unclear when asked in an urgent question in the Commons this morning.

He said reports have suggested the vessel did have a licence, but it was subsequently removed from a list and it is not understood why.

He also said he was working with Marine Scotland and the Scottish Government to resolve the situation.

Asked about the vessel this afternoon, the Prime Minister’s spokesman said the government was “continuing to contact French authorities” and added: “Our ambassador is in touch with the French Europe minister, the Secretary of State for Environment, Food and Rural Affairs is in contact with his French opposite number and we will provide further details as more information becomes available. “We are still working to understand the details.”

He said that threats being made by France to potentially disrupt electricity supplies to the UK were “disappointing and disproportionate and not what we'd expect from a close ally and partner”.

The threats have been escalating for weeks, amid anger in France after the UK and Jersey turned down applications from dozens of French boats to fish in their waters in what France said was a breach of Britain’s post-Brexit trade deal with the EU.

French ministers have warned they will block British boats from some French ports and tighten checks on vessels travelling between France and the UK if the issue is not resolved by Tuesday.

The Prime Minister’s official spokesman said the UK fully supported the way Jersey and Guernsey were handling the issue, which was “entirely in line” with the provisions of Britain’s trade deal with the EU.

“We are monitoring this situation very carefully. We have relayed our concerns to the (European) Commission and the French government,” the spokesman said.

“We think the threats outlined yesterday evening were disappointing, were disproportionate and were simply not what we expect from a close ally and partner.

“I can’t at this moment set out exactly what our response might be. It will be appropriate, it will be calibrated.

“We want to have further discussions with French government and the EU. We stand ready to respond appropriately.”