On Saturday, Mr Johnson said there was “some turbulence in relations” with France following Mr Castex’s letter, which said it was “essential to make it clear … that it is more harmful to leave the union than to stay in it “.
He suggested that as early as this week, Britain could trigger the dispute mechanism in the trade agreement between Britain and the EU after Brexit over fisheries with France.
After Mr Johnson’s meeting with Mrs von der Leyen at the G20 summit in Rome, a spokesman for Downing Street said: “The Prime Minister … raised his concerns over the rhetoric of the French Government in recent days over the issue of fishing licenses.
“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 broader international law.”
A senior government source said: “The letter definitely raises a question of how the EU is acting and whether it is acting in good faith around the negotiations.”
Nr. 10 ‘worried and surprised’ over French response
Lord Frost, Britain’s Brexit negotiator, later tweeted that the government was “concerned and surprised” by Mr Castex’s remarks, adding: “I hope this opinion is not more widespread in the EU. To see it expressed this way is clearly very worrying and very problematic in the current context as we try to resolve many very sensitive issues, including on the Northern Ireland Protocol.
“It is all the more so that the threats that France has made this week against our fishing industry, against the energy supply and against future cooperation, for example through the research program Horizon, are unfortunately part of a pattern that has lasted at large. parts of this year. “
The French threats followed anger in Paris over decisions by Britain and Jersey to deny fishing licenses to dozens of French boats in order to gain access to British waters. France has warned it will take retaliatory action if the dispute is not resolved by Tuesday.