London: A super-trawler that was banned from fishing in Australian waters is being investigated after reportedly dumping more than 100,000 dead fish in the Atlantic Ocean.

The Dutch-owned trawler FV Margiris – the world’s second-largest fishing vessel – spilled its catch after its net ruptured, according to the industry group that represents the vessel’s owner.

In a statement, the Pelagic Freezer-Trawler Association (PFA) said the spill occurred “involuntarily” on Thursday and was a “very rare occurrence”.

But French authorities have opened an investigation after an environmental group disputed this account, saying it was an illegal discharge.

Annick Girardin, France’s maritime minister, called the images of the dead fish “shocking”, and has asked the country’s national fishing surveillance authority to launch an inquiry.

The vessel, which is 14 times larger than UK fishing boats, was banned from Australian waters for two years in 2012 due to concerns about its effect on local stocks. It was later accused of plundering fish from the sea around Britain before Brexit.

The French arm of the campaign group Sea Shepherd first published images of Margiris’ spill, showing the ocean’s surface covered by a dense layer of blue whiting - a sub-species of cod used to mass-produce fish fingers, fish oil and meal.

Sea Shepherd France said it did not believe the incident was accidental, but rather an attempt by the trawler to discharge a type of fish that it did not want to process. It is a practice known as discharging bycatch, which is banned under EU fishing rules.