Why France and UK are fighting over fishing - and how a post-Brexit trade war could erupt

Relations between the UK and France have sunk to a historic low amid a dispute over fishing and a "costly trade war" could erupt if tensions between the two allies do not ease.

A British trawlerman has been charged by France, the French ambassador has been summoned by the UK - and it's all over a disagreement between the two nations on the rights of vessels to fish in each country's water.

France is threatening to block British boats from its ports if the UK does not allow more of its vessels to use British waters, but Boris Johnson's government says it will retaliate with "proportionate" measures if necessary.

Here we take a look at the fishing dispute and how it could result in a trade war between the two previously friendly nations.

Why was the British trawler detained and its skipper charged?

The scallop vessel Cornelis was ordered to divert to the port of Le Havre on Thursday after the French authorities said it was fishing in French waters without a licence.

On Friday the boat's skipper was charged with not having a licence to fish in French waters.

A source close to the seized vessel has told ITV News the situation could still be resolved if the UK's Marine Management Organisation can explain to French authorities why the licence doesn’t appear on the list.

The boat's skipper will appear in court in Le Havre in August 2022 if an explanation is not provided.

The trawler will only be allowed to leave France if the issue around its paperwork is resolved, or if a bond is paid allowing the vessel to depart.

The French said that another British trawler had been fined for obstruction after refusing to allow police to board to carry out checks.

The owner of the Cornelis, Macduff Shellfish, said the vessel had been fishing legally in French waters and called on the British Government to protect the rights of British fishermen.

What is the wider context of the fishing dispute - will there be a trade war?

ITV News Political Editor Robert Peston says tensions over fishing "could escalate into a costly trade war" if a resolution is not found.

Fishing has been a major point of contention between the UK and the EU during and after Brexit negotiations, with the two sides struggling to agree on future rights in European waters.

Previous tensions with France over fishing rights prompted Royal Navy ships to be scrambled to Jersey amid concerns of a blockade of the island.

Most recently, the UK and Jersey turned down applications from dozens of French boats to fish in their waters in what Paris said was a breach of Britain’s post-Brexit trade deal with the EU.

Peston says the concern for Boris Johnson is France's threat to "cut off electricity supply to Jersey and introduce significant and costly new bureaucracy for truck drivers going between France and the UK".

What have the French said about the latest incident?

French ministers have warned they will block British boats from some French ports and tighten checks on vessels travelling between France and the UK if the issue is not resolved by Tuesday.

France’s Europe minister, Clement Beaune, told French TV news channel CNews: “We have been extremely patient. Our fishermen have been extremely responsible.

“And so, from November 2, it’s over. We will engage in dialogue if the British want to, but we are taking retaliatory measures.”

How has the UK responded?

Environment Secretary George Eustice said the French threats appeared to breach international law and warned the UK would respond in an “appropriate and calibrated” manner if they were carried out.

"If they do bring these into place, well, two can play at that game and we reserve the ability to respond in a proportionate way," Environment Secretary Eustice told Sky News.

In an emergency Commons statement, Mr Eustice said the vessel had been granted a licence by the EU but there were reports that it subsequently had been removed from the list of vessels permitted to fish in French waters for reasons that were unclear.

Mr Eustice said the UK has licensed 98% of EU vessels that have applied for access post-Brexit and more are expected to be granted following “constructive” talks with the European Commission.

How did Brexit spark the fishing feud?

When the UK left the EU, it also left the common fisheries policy, which since 1970 has allowed members access to European waters outside the first 12 nautical miles of each country’s coastline.

The Brexit deal outlined how EU boats could continue to fish in UK waters, but British fishermen would get a greater share of fish from domestic waters.

Most of the share is being transferred to the UK this year, and there will be annual negotiations to decide how the catch is shared out going forwards.