"Aside from a few exceptions, all French ports will no longer be accessible to British boats," France's European affairs minister, Clement Beaune, said in an interview on French TV station CNEWS, referring to vessels that offload fish and produce.
Some three or four ports would remain open to British fishing vessels when the closure comes into force on Tuesday, with the exact number decided in the week ahead, he said, adding: "There will be no tolerance, no indulgence."
Beaune also said that security checks begun on Wednesday night had intercepted two British vessels "that were not respecting the rules."
The French minister for the sea, Annick Girardin, had earlier confirmed that two British vessels had been stopped and fined, with one diverted to a French port.
One of the boats was not listed on the European Union's approved list of UK fishing vessels, and the regional government director "immediately issued" an order to divert the vessel to the French port of Le Havre, her statement said.
A UK government spokesperson said the proposed French actions were "unjustified" and "do not appear to be compatible" with the Brexit agreement or wider international law.
"We regret the confrontational language that has been consistently used by the French government on this issue, which makes this situation no easier to resolve," the spokesperson said in a statement, adding that the government has decided to summon the French Ambassador.
The other boat was fined for not complying with orders to allow French authorities to board the vessel to conduct checks, the statement tweeted by Girardin said. Additional checks by French maritime gendarmes found no further infraction of fishing regulations.
The boats were stopped off the coast of Le Havre, in the English Channel. Legal proceedings could see the first vessel's catch and the boat itself confiscated against the payment of bail, the statement said, adding that, "the captain of the fishing vessel risks criminal sanctions."
The fines represent the latest round of tensions in long-running disputes between the UK and France over the rights of French and British vessels to fish in each country's waters following Brexit.
The latest French measures come in response to the UK government's refusal to grant post-Brexit fishing licenses to several French fishermen. Beaune said that nearly half of French applications to fish in British waters had been refused; an EU commission spokesperson told journalists on Tuesday that as of October 1, the UK has granted licenses to 15 out of the 47 smaller French vessels that applied to fish in UK territorial waters.
Of the remaining vessels, France has agreed to rescind applications for 17 vessels whose evidence of their fishing activity in British waters pre-Brexit was considered poor, the spokesperson said.
French Prime Minister Jean Castex told reporters Thursday that roughly 40% of French applications to fish in British waters had not yet been granted, this number varying according to fishing zones. A UK government spokesperson however said on Thursday that 98% of license applications from EU vessels to fish in UK waters had been delivered.
"Our ministers are working on this around the clock, but at the same time, I want to tell the British government that we will make sure that our interests are respected and that our word is kept," the Castex said.
He added that he would like to see a "de-escalation" but the the British government had "all the keys to achieve it."
A French government statement said "targeted measures" against the UK from November 2 would also include a strengthening of customs and sanitary checks, systematic security checks of British vessels and a strengthening of checks on trucks traveling to and from the UK.
Beaune added that "systematic checks" on trucks would also include their cargo, adding that these was not designed to "cut contact, access but to be extremely strict regarding inspections."
"This is not a war, but a fight," Girardin told French radio station RTL Thursday morning. A second series of French retaliatory measures is being prepared, a government statement said, adding that, "in this context, France does not exclude re-examining the supply of energy provided to the UK."
"Now we must speak the language of force because because ... this British government only understands this," Beaune said. "We cannot be in a climate of confidence with a neighbor, a partner who doesn't respect the rules."
The UK government said on Wednesday, before the latest measures were announced, that it would be relaying its concerns to the European Commission and French government.
A Commission spokesperson said in a statement Thursday that the EU would continue discussions with both the UK and France in order to resolve the issue.
The EU emphasized that "all French vessels entitled to a license should receive one," according to the statement.
They also affirmed that their "Trade and Cooperation Agreement with the UK is clear: vessels who were fishing in these waters should be allowed to continue."