Boris Johnson has not ruled out triggering the dispute mechanism against France as a row between the two countries over post-Brexit fishing rights escalates.

On Friday, France seized a British scallop trawler and threatened to block ports and increase checks on boats and lorries over the UK denying some boats a licence to fish in Jersey’s waters.

French President Emmanuel Macron raised tensions further with the UK after telling the Financial Times that the UK is risking its “credibility” after going back on commitments made to the EU with regards to fishing.

Speaking to Sky News’ Beth Rigby on Saturday ahead of the G20 summit in Rome, the PM reiterated that he will “do what is necessary to protect British interests” if ministers believe the French have breached the UK-EU trade agreement.

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Addressing the diplomatic dispute, Mr Johnson admitted to Sky News that he is “worried” that the French may have broken the treaty with regards to fishing.

Pressed on whether he could rule out triggering the dispute mechanism against the French next week, the PM added: “No, of course not, I do not rule that out.”

The dispute process would see a consultation period started, after which, if there is no solution found, an arbitration panel would be formed with compensation demanded or even the treaty suspended as punishment, according to the Commons Library.

The row erupted after the UK authorities refused to give licences to 55 French fishing vessels to fish in UK waters because they believed they did not meet the requirements.

But the French claim the British are in the wrong and had threatened to make it difficult for UK fishers and lorry drivers in France.

Tensions escalated further after a British scallop trawler – named the Cornelis Gert Jan – was detained in Le Havre on Thursday.

Andrew Brown, head of public affairs for Macduff Shellfish, which owns the boat, said the charge “relates to fishing in French waters without a licence and that’s the bone of contention”.

“We believe we were fishing with a valid licence and the French authorities don’t,” he said.

As well as detaining the scallop trawler, France has also fined two other fishing vessels over the row.

Mr Johnson said: “If another European country wants to break the TCA – the Trade and Cooperation Agreement – then obviously we will have to take steps to protect UK interests.”

“We are very keen to work with our friends and partners on all these issues,” he told Beth Rigby.

Pressed on whether the UK will launch a dispute settlement with France next week after Brexit minister Lord Frost told the EU on Friday that the UK government could launch proceedings if France goes ahead with its threats over the fishing row, the PM said: “If there is a breach of the treaty, or if we think there is a breach of the treaty of course we will do what is necessary to protect British interests.”

Asked if he believes there has been a rule-break, Mr Johnson said: “I am worried that there might be – and I am looking at what is going on at the moment, and I think that we need to sort it out.”

Mr Johnson said the UK government “want to see that treaty observed”, but added that “the much more important issue” before world leaders today is climate change.

The PM and President Macron came face-to-face at the G20 summit in Rome this weekend and will do again at the COP26 climate conference in Glasgow.

Speaking on Friday, a Downing Street spokesman said Mr Johnson will have a “brush by” with the French president about the row at the COP26 climate summit in Glasgow, which starts on Sunday.

The spokesperson added that threats to “disrupt UK fisheries and wider trade, to threaten energy supplies… would put the European Union in breach of the Trade and Cooperation Agreement”.

Meanwhile, a letter seen by Sky News shows the French Prime Minister Jean Castex urging the EU to prove that there is “more damage to leaving the EU than to remaining there”.

In the letter to European Commission President Ursula von der Leyen, dated 28 October, Mr Castex states: “It’s 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.”

Mr Castex adds that the EU must demonstrate its “total determination” to force the UK to stick to the agreements it has made on fishing.

France says the decision from the UK and Jersey in September to deny fishing licences to French boats was a breach of the Brexit deal.

French officials have warned that they will prevent British boats from landing their catches in some French ports next week unless the row is resolved by Tuesday.

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Speaking to Sky News on Friday, Environment Secretary George Eustice said 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 trade and co-operation agreement with the EU.

As well as detaining the scallop trawler, France has also fined two other UK fishing vessels over the dispute.

Mr Eustice said: “We don’t know what we’ll do, they said they wouldn’t introduce these measures until Tuesday at the earliest, we’ll see what they do.

“But if they 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.”

The French ambassador to the UK was summoned to Downing Street on Thursday over the issue.