French authorities in Le Havre allege the Cornelis Gert Jan vessel did not have a licence, a claim the boat's owner Macduff Shellfish denies. The European Union also claimed the UK authorities withdrew the licence on March 1.

       But sources close to the owners of the fishing vessel told ITV West Country that the skipper has shown his licence to fish in French waters, which has satisfied local authorities.

       But an administrative “spreadsheet error” at the Government's Marine Management Organisation (MMO) meant the vessel was still being held in France, they reported.

       France is threatening to block British boats from its ports and tighten checks on vessels if an issue over a lack of licences for small French vessels to fish in British waters is not resolved by Tuesday.

       The UK has said it could retaliate if France carries out its hardline stance.

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