Two Royal Navy vessels are patrolling waters around Jersey as dozens of French boats gathered near the island’s main port in protest over post-Brexit fishing rights.

HMS Severn and HMS Tamar have been deployed by the UK Government to “monitor the situation” surrounding the Channel Island amid concerns of a possible blockade at the port of St Helier.

French fishing vessels gathered near the harbour on Thursday morning, with some crews setting off flares, in protest against a new post-Brexit licensing system implemented last week.

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

Prime Minister Boris Johnson spoke to Jersey chief minister John Le Fondre and external affairs minister Ian Gorst on Wednesday, and “underlined his unwavering support” for the island.

Downing Street said the two Royal Navy ships were sent as a “precautionary measure” and the UK and Jersey governments would continue to work closely on the issue.

Jersey fisherman Josh Dearing described the scene at St Helier on Thursday morning as “like an invasion”, with the French fleet mostly made up of “big French dredgers and trawlers” of 12 metres or more.

It was quite a sight. It was like an invasion

The 28-year-old told the PA news agency: “There were probably about 60 boats. There were a few hand-held flares and smoke flares going off and apparently a few maybe bangers and stuff going off from the French.

“It was quite a sight. It was impressive, I looked from the shore this morning and it was just like a sea of red lights and flares already going off at sea. It was like an invasion.”

Later on Thursday morning, the Jersey Evening Post 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.

The row began after Jersey implemented new requirements under the terms of the UK-EU trade deal for boats to submit evidence of their past fishing activities to receive a licence to carry on operating in Jersey waters.

Don Thompson, president of the Jersey Fishermen’s Association, said his members have warned they are prepared to ditch their fishing licences if the French win their demands.

He told Good Morning Britain: “We’ve already told our minister – our licences, some of our fishermen have paid a quarter of a million pounds for our licences – we’re going to get rid of our licences and fish without licences.

“We just will not put up with those (French) boats being left to fish uncontrolled, unsustainably, in our waters whilst we’re subject to all sorts of constraints.”

On Wednesday, Mr Gorst held talks with Marc Lefevre, president of the La Manche region of northern France, on the “difficult set of issues relating to fishing licences”.

“There are a number of important matters which we will continue to work through,” he said.

Ms Girardin told the French parliament the dispute gave Paris the “means” to act against the island if the issue could not be resolved, adding: “Even though I am sorry that it has come to this, we will do so if we have to.”

But Mr Gorst said the island is not seeking to bar boats which have historically fished in Jersey waters and insisted the dispute can be resolved amicably.

He said that of the 41 boats which sought licences under the new rules last Friday, all but 17 had provided the evidence required.

“The trade deal is clear but I think there has been some confusion about how it needs to be implemented, because we absolutely respect the historic rights of French fishermen to fish in Jersey waters as they have been doing for centuries,” he said.

“I do think a solution can be found. I am optimistic that we can provide extra time to allow this evidence to be provided.”