A spokesman for the British Department for Environment, Food and Rural Affairs (Defra) told The Guardian: "We are clear that Jersey is responsible for its own territorial waters".
Dimitri Rogoff, president of the regional fishing committee of Normandy in northern France, said that if French fishermen continued to be blocked from the waters off Jersey, there should be reprisal measures.
HMS Tamar (REAR), a Batch 2 river-class offshore patrol vessel of the British Navy, is watched by a fishing boat as it patrols the waters off the British island of Jersey on May 6, 2021.
The Commodore Goodwill was delayed by over four hours when a flotilla of around 70 French fishing boats blockaded the island's main harbour.
Meanwhile, No 10 said, in a call with Jersey officials, Prime Minister Boris Johnson had given his "unequivocal support" for the island and confirmed that the two Royal Navy vessels would "remain in place to monitor the situation as a precautionary measure".
Jersey is the largest of the Channel Islands in the English Channel and, while geographically closer to France, is a British Crown Dependency.
"We are working closely with the European Union and Jersey on fisheries access provisions following the end of the Transition Period so trust the French will use the mechanisms of our new treaty to solve problems".
Girardin described the new restrictions as "absolutely unacceptable", and said: "If we accept this for Jersey, it would imperil our access everywhere".
The maritime prefecture of Manche and mer du Nord told the BBC the two French vessels were not on military missions.
"We want to be able to return to negotiations, that we can obtain the fishing licenses provided for in the agreement".
The Jersey spat is part of an escalating dispute between the European Union and the United Kingdom over fishing rights, with boats from both sides facing administrative hurdles and being turned away over paperwork. Paris has accused the British government off using red tap to limit fishing which French leaders claim is in breach of the agreement made in negotiations past year.
Jersey issued 41 licences for access to its waters on Friday when an interim agreement came to an end.
The row emerged over a new licensing system for French fishing vessels introduced by the Government of Jersey under the UK-EU Trade and Cooperation Agreement (TCA).
But the French government claimed the list of approved ships came with further demands that "were not arranged or discussed, and which we were not notified about".
Girardin said Wednesday in Le Parisien newspaper that Jersey's requirements are "not acceptable".
He said: "I see it as very much an insult to them and they are extremely upset. Nothing about what species were caught, nothing about if you've fished for 20 days or 30 days [and having to] prove that".
Ian Gorst, said Jersey was just following new rules that took effect last week.
Gravity Industries's jetpack is trialled by the UK Royal Marines.
The ships are routinely used for fisheries protection - with sailors able to board other boats for spot checks.