Jersey has the UK government’s “unequivocal support”, Downing Street has said, amid an ongoing row with France over post-Brexit fishing rights.

Two Royal Navy vessels are patrolling waters around Jersey amid concerns of a possible blockade of the island.

HMS Severn and HMS Tamar have been deployed to “monitor the situation” at the Channel Island amid a protest by French fishing vessels at the port of St Helier over the lack of access.

France has also despatched two patrol boats to the area.

A Downing Street spokesperson said on Thursday Boris Johnson spoke to the chief minister of Jersey, senator John Le Fondré, this morning.

“The chief minister updated the prime minister on the latest developments with French fishing vessels around Jersey’s coast,” No.10 said.

“The prime minister reiterated his unequivocal support for Jersey and confirmed that the two Royal Navy Offshore Patrol Vessels would remain in place to monitor the situation as a precautionary measure.

“They agreed to stay in touch as the situation develops.”

French maritime minister Annick Girardin warned on Tuesday that the country is ready to take “retaliatory measures”, accusing Jersey of dragging its feet over issuing new licences to French boats.

Dozens of French boats arrived at the harbour on Thursday morning, with some crews setting off flares during the so far peaceful protest, according to the Jersey Evening Post.

The newspaper later said the leader of the protest had asked the French boats to leave the harbour to let a freight ferry, the Commodore Goodwill, depart.

Paris has warned it could cut off power to the island, which receives 95% of its electricity from France through three undersea cables, in retaliation for the fallout.

A Ministry of Defence spokesman said: “HMS Severn and HMS Tamar are deploying to Jersey to conduct maritime security patrols. This is a strictly precautionary measure and has been agreed with the Jersey Government.”