If France follows through with threats to cut off energy supplies, the UK Government may force French vessels to be docked and inspected under new rules. Officials may also introduce measures for French vessels to come to port and submit customs declarations. As well as having their catch inspected, officials may also instruct the Marine Management Organisation to increase checks on licences, nets and equipment at sea.

       One Government source told The Daily Telegraph: "We are looking at the options and would be ready to act."

       Discussions between UK and French officials will continue on Tuesday after Emmanuel Macron stepped back from introducing measures on Monday evening.

       Lord Frost will travel to Paris this week for talks with EU minister Clement Beaune.

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