- Oops!Something went wrong.Please try again later.
The prime minister has sought to soothe relations between France and the UK, telling journalists en route to the G20 in Rome that France is one of the UK's "best, oldest, closest friends and allies".
An ongoing row about post-Brexit fishing licences has deepened in recent days, while there was anger in Paris last month over a security partnership between the UK, US and Australia that saw the latter pull out of a major contract with France for submarines.
In a letter written to the European Commission president Ursula von der Leyen, which has been seen by Sky News, French prime minister Jean Castex described the UK's attitude to fishing rights as "non-cooperative" and said it is "essential to clearly show to European public opinion that respecting commitments isn't negotiable and that it's more damaging to leave the European Union than to stay in it".
Asked what he would say to President Emmanuel Macron when the pair meet in Rome this weekend, Mr Johnson responded: "[The] ties that unite us, that bind us together, are far stronger than the turbulence that currently exists in the relationship.
"That is what I will say to Emmanuel, who has been a friend for many years.
"And what I will also say is that there may be people on either side of the Channel that think they have an interest in promoting disharmony between the UK and France and creating the impression of disharmony. I don't think Emmanuel shares that perspective."
On the issue of retaliation, the prime minister said he was "puzzled about what was going on, and we fear there may be a breach of the trade and cooperation agreement" and "we will stand by to take the appropriate action".
Asked if the UK would back down on fishing licences, the PM said "we will do whatever is necessary to ensure UK interests" are protected.
Mr Johnson said he would be "surprised" if the French snarled up trade across the Channel.
"I haven't heard that from our French friends, I would be surprised if they adopted that approach," he said.
The PM told reporters that UK fishermen should be confident in going about their lawful business, wherever that will be.
Speaking to the Financial Times, Mr Macron said Britain's credibility was on the line in the dispute.
"Make no mistake, it is not just for the Europeans but all of their partners," the French president said regarding fishing rights.
"Because when you spend years negotiating a treaty and then a few months later you do the opposite of what was decided on the aspects that suit you the least, it is not a big sign of your credibility."
The comments come after Brexit minister Lord Frost threatened to retaliate in the escalating row with "practical responses".
Lord Frost said he made clear to EU Brexit negotiator Maros Sefcovic if France carried through with "unjustified" threats to disrupt fisheries and hauliers next week, the UK would react "accordingly", in both physical and legal ways.
The pair were holding talks in London about the Northern Ireland Protocol, but the row over licences for French boats to fish in UK waters dominated.
Asked about the protocol and whether he would trigger Article 16, a move to suspend cooperation on Northern Ireland, the PM said: "I believe the answers to the problems of the movement of goods east-west in our country, from Great Britain to Northern Ireland, should be very simple.
"I think we need to fix it. I'm not convinced that the solutions we're seeing do fix it.
"We will have to take the steps that are necessary to protect the territorial integrity of the UK and the UK's internal market."
The fishing dispute took a turn for the worse on Thursday when France seized a British scallop trawler and later charged its captain.
The skipper told Sky News on Friday evening that the vessel would not be leaving for now.
"Your guess is as good as mine," he said as he left the scene with a lawyer. It is not clear why he had to leave the trawler.
The row kicked off after the UK refused to give licences to 55 French fishing vessels to fish in UK waters because they did not meet the requirements, the UK said.
But the French claim the British are in the wrong and threatened to make it difficult for UK fishers and lorry drivers in France before detaining the Cornelis Gert Jan.
There are two other British crew members on the Cornelis, and they have all been told to remain on the boat for their own safety as tensions continue.
If the UK does not grant licences for 55 French vessels, France has said from next Tuesday it will block its ports, carry out security checks on British vessels, reinforce controls on lorries to and from the UK, reinforce customs and hygiene controls, and raise tariffs.
There has also been a threat of halting electricity to the Channel Islands, which are British dependencies but are close to the French coast.
A UK government spokesman said Lord Frost "made clear" to Mr Sefcovic if those threats are carried out, the EU would be in breach of the Trade and Cooperation Agreement (TCA) between the UK and the bloc.
He added: "The government is accordingly considering the possibility, in those circumstances, of launching dispute settlement proceedings under the TCA, and of other practical responses, including implementing rigorous enforcement processes and checks on EU fishing activity in UK territorial waters, within the terms of the TCA."
Earlier, environment secretary George Eustice told Sky News the UK has issued post-Brexit licences to 1,700 vessels, including 750 French fishing boats, which amounts to 98% of applicants.
He said the remaining 55 vessels, despite the UK trying to help them with the data, could not prove they had fished in Jersey's waters previously so could not get a licence under the trading agreement with the EU.
Mr Eustice also told Sky News: "If they [the French] do bring these measures into place, well, two can play at that game, and we obviously reserve the ability to respond in a proportionate way."