News of the sum emerged on Monday and follows the Scottish skipper of the Cornelis Gert Jan being told that he faces a fine of more than £63,000 if convicted following a criminal trial next year.
It also came as the the British Foreign Secretary increased the rhetoric over the squabble, by giving the French government a 48-hour deadline to withdraw threats against Britain over post-Brexit fishing licences.
Liz Truss blasted “completely unreasonable threats” to the fishing industry and threatened to sue France under the terms of the Brexit deal.
“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, as the Anglo-French relationship was heading for Brexit meltdown on the first day of the UN COP26 climate summit, which the UK is hosting.
She was speaking after the Seine-Maritime prefecture confirmed that the Cornelis would remain in the Normandy port of Le Havre unless its crew paid “a 150,000 euros deposit” – the equivalent of more than £125,000.
A spokesperson said: “The boat will not be allowed to leave until that sum is paid.”
It far outweighs anything the boat might have earned during what started off as a five-day trip to France to fish for scallops.
The boat was detained by gendarmes last Wednesday, and escorted to the quayside at Le Havre, where they have remained every since, sparking a diplomatic incident.
Its skipper, who has not been formally named, has been charged with “acts of unauthorised sea fishing in French maritime salt waters by a third-party vessel to the European Union”.
Prime Minister Boris Johnson and French President Emmanuel Macron discussed the growing diplomatic row at the G20 in Rome at the weekend.
Mr Johnson said he had been “puzzled” to read a letter from Paris to the EU which, he claimed, asked “for Britain to be punished for leaving the EU”.
Referring directly to Brexit, the Prime Minister said: “I don’t believe that is compatible either with the spirit or the letter of the Withdrawal Agreement of the Trade and Cooperation Agreement and that’s probably all I’ll say about that.”
In turn, Mr Macron said: “I don’t want escalation. We need to be serious. I don’t want to have to use retaliation measures because that wouldn’t help our fishermen.”
Mr Macron said Paris had offered proposals to London and “now the ball is in Britain’s court”.
France’s European minister Clement Beaune said the current row was “a breach” of the Brexit agreement and that it was a “political choice” on London’s part.
With no side backing down and stalemate looming, Tuesday could see a major escalation in the crisis.
Andrew Brown, director of Scottish firm MacDuff Shellfish, which own the Cornelis, said the boat was being used as a “pawn” by the French, and had not acted illegally.
Mr Brown said last week: “We are looking to the UK government to defend the rights of the UK fishing fleet and ensure that the fishing rights provided under the Brexit fishing agreement are fully respected by the EU.”
On Monday morning, the Cornelis was still moored in Le Havre, with its crew of eight on board.
The boat headed out from Shoreham, Sussex, early last Tuesday morning.
Her seizure is the latest move by France in an ongoing row with the UK over who has rights to fishing grounds in the Channel now Britain has left the EU.
Clement Beaune, France’s Europe minister, has said “we need to speak the language of force” to Britain because it is “the only thing this government understands”.
He was immediately accused of “sabre rattling” by British critics, as was Annick Girardin, the Maritime Minister in Paris, who said: “It’s not war, but it is a fight.”