Foreign Secretary Liz Truss has given France a no-nonsense rebuke to the French President over a a fishing rights row.
Ms Truss rejected the deadline set by Emmanul Macron for more French boats to be licences to fish in British waters.
She countered with the UK Government is prepared to start action over breaches in the post-Brexit trade deal.
She added that Mr Macron was only attacking the UK because it might help his re-election chances next year.
Ms Truss told Sky News:
“The deal hasn’t been done, the French have made completely unreasonable threats, including to the Channel Islands and to our fishing industry and they need to withdraw those threats, or else we will use the mechanisms of our trade agreement with the EU to take action.”
She said Britain would use the dispute resolution mechanism under the post-Brexit trade deal to seek “compensatory measures”.
She added: “That is what we will do if the French don’t back down.
“Stop threatening UK fishing vessels, stop threatening the Channel ports and accept we are entirely within our rights to allocate the fishing licences in line with the trade agreement.
“This issue needs to be resolved in the next 48 hours.
“We’re not simply going to roll over in the face of these threats.”
Ms Truss suggested Mr Macron might be making “unreasonable threats” because of the looming election.
She said: “You might say there’s a French election coming up.”
The French have warned they will block UK fishing boats from some of its ports.
They will also tighten up check on lorries – creating lengthy delays – entering France laden with British goods.
Earlier at a G20 press conference in Rome Prime Minister Boris Johnson said:
“On fish, I’ve got to tell you the position is unchanged.
“And I’ll just say this, for the record. I must say I was puzzled to read a letter from the French Prime Minister explicitly asking for Britain to be punished for leaving the EU.
“I just have to say to everybody I don’t believe that that is compatible either with the spirit or the letter of the Withdrawal Agreement or the Trade and Cooperation agreement, and that’s probably all I’ll say about that one.”