Boris Johnson demands EU rein in Emmanuel Macron –

On Saturday, Mr Johnson said there was “some turbulence in the relationship” with France following Mr Castex’s letter, which stated that it was “essential to make clear… that leaving the union is more damaging than remaining in it”. 

He hinted that Britain could trigger the dispute mechanism in the post-Brexit UK-EU trade agreement as soon as this week over the fishing row with France.

Following Mr Johnson’s meeting with Mrs von der Leyen at the G20 summit in Rome, a Downing Street spokesman said: “The Prime Minister… raised his concerns about the rhetoric from the French government in recent days over the issue of fishing licences. 

“The Prime Minister stressed that the French threats are completely unjustified and do not appear to be compatible with the UK-EU Trade and Cooperation Agreement or wider international law.”

A senior government source said: “The letter definitely raises a question of how the EU is acting and whether or not it is acting in good faith around the negotiations.”

No 10 ‘concerned and surprised’ by French response

Lord Frost, the UK’s Brexit negotiator, later tweeted that the Government was “concerned and surprised” by Mr Castex’s remarks, adding: “I hope this opinion is not held more widely across the EU. To see it expressed in this way is clearly very troubling and very problematic in the current context when we are trying to solve many highly sensitive issues, including on the Northern Ireland Protocol.

“This is all the more so as the threats made by France this week to our fishing industry, to energy supplies, and to future cooperation, eg through the Horizon research programme, unfortunately form part of a pattern that has persisted for much of this year.”

The French threats followed anger in Paris over decisions by the UK and Jersey to deny fishing licences to dozens of French boats to access British waters. France has warned that it will take retaliatory action if the dispute is not resolved by Tuesday.