The war of words between France and the UK over fishing intensified on Saturday.
The UK government said it was "actively considering" launching legal action under the Brexit deal if France carried out its threat to increase customs checks as the countries dispute over fishing licences.
Brexit minister David Frost said the UK was "actively considering launching dispute settlement proceedings" over the fishing row and urged the "EU and France to step back from rhetoric and actions that make this more difficult."
The French government has said that it is still waiting on obtaining a number of fishing licences and has accused London of not respecting the Brexit deal which said that fishermen could continue to fish in British waters if they obtained a licence and proved that they previously were fishing there.
France threatened to increase customs checks on goods coming across the Channel from November 2, including a ban on British fishing vessels at ports and increased checks on trucks, which could slow down trade.
They also threatened to introduce measures related to electricity supplies to the Channel Islands, British Crown dependencies that lie off the coast of France and are heavily dependent on French electricity.
The back and forth between the two countries escalated on Saturday, with Frost tweeting that "recent French rhetoric and threats" constitute a potential "breach by the EU of its Treaty obligations."
UK Prime Minister Boris Johnson admitted to the BBC that there was "some turbulence in the relationship" with France, but insisted that the issue was "dwarfed" by the agenda that unites the countries.
Earlier in the day, French President Emmanuel Macron was quoted as saying that the UK's "credibility" was at stake.
"Make no mistake, it is not just for the Europeans but all of their partners. 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," Macron said in an interview with the Financial Times, the newspaper reported.
Macron said he was sure that Britain has the "good will" to solve the dispute. "We need to respect each other and respect the word that has been given," he said, according to the FT.
In a letter to the European Commission that was leaked to the press, French Prime Minister Jean Castex reportedly appealed to the EU to back France in the dispute, saying they should show that “leaving the Union is more damaging than remaining in it."
Frost called Castex's comments “troubling” and accused France of a pattern of threats "to our fishing industry, to energy supplies, and to future cooperation."
Macron and Johnson are set to meet on the sidelines of the G-20 summit in Rome this weekend.
While travelling to the summit, Johnson attempted to calm the waters over the dispute, calling France "one of our best, oldest, closest allies, friends and partners".
Calling Macron a "friend," Johnson said some people in both countries may be trying to stir up disharmony between the UK and France, but “I don’t think Emmanuel shares that perspective.”
But he also reiterated Britain’s willingness to respond to any violations of its divorce deal with the EU.
The UK summoned the French ambassador to voice its displeasure after French authorities fined two British fishing vessels earlier in the week.
This article has been updated with comments from UK officials.