Spain's Supreme Court said Tuesday it had found the captain, British insurer and owner of an oil tanker that broke up off northwestern Spain in 2002 liable for one of Europe's worst environmental disasters.

Reversing an earlier decision acquitting the ship's Greek captain Apostolos Mangouras, the court sentenced the skipper to two years' jail and also found mutual insurance company The London P&I Club liable for the disaster, as well as ship owner Mare Shipping Inc.

The total cost of the damage has been estimated at 4.1 billion euros ($4.4 billion) and by designating those liable for the disaster for the first time, Spain's top court finally opens the way for compensation more than 13 years after the spill.

The Prestige tanker ran into trouble in rough seas in November 2002.

Six days later, damaged and adrift, it broke in two and sank off the coast of Galicia.

The accident saw 63,000 tonnes of oil spill into the sea and blacken 2,980 kilometres (1,852 miles) of shoreline in Spain, France and Portugal with sludge.

The spill caused huge damage to wildlife and the environment, as well as to the region's fishing industry, leading to an international cleanup effort.

- Ageing, malfunctioning ship -

A Spanish court in 2013 acquitted Mangouras and the ship's chief engineer, as well as a senior Spanish official, of environmental crimes over the wreck, arguing they did not act intentionally or with serious negligence.

But the Supreme Court revoked the acquittal for Mangouras, accusing him of "gross negligence" for having sailed at a time when bad weather was possible, knowing that the ship was old and that the automatic pilot no longer worked, for instance.

Mangouras' seamanship was not only dangerous, "he also created a serious risk, particularly with regards to the highly-polluting nature of the substance he was transporting," it concluded.

The London P&I Club, meanwhile, could be liable for up to $1 billion (920 million euros), though no sum has yet been decided.

The acquittals in 2013 had caused an uproar, with thousands protesting in Galician cities.

Greenpeace had said that the decision provided "a carte blanche to the oil industry to threaten the environment and citizens".

And Spain's State Prosecutor Luis Navajas, who asked the Supreme Court to overturn the acquittals in September, called the decision "flawed" and "notoriously wrong."

Among the evidence he said had been overlooked were notes from the Prestige's former captain, Stratos Kostazos, who had complained that the tanker was in bad shape and had refused to sail in it.

The Supreme Court said Tuesday that two major energy companies -- Spain's Repsol and Britain's BP -- had advised against using the Prestige tanker, a 26-year-old vessel with a carrying capacity of 81,000 tonnes.

It added that a man who had worked for the company that managed the Prestige said the owners of the ship knew what state it was in and had dispatched it to Saint Petersburg to "die."

"But... it was decided it would make another sea crossing, which really was its final one," the court wrote in its statement.

- 'Scapegoat' -

Still, Tuesday's announcement was not met with much enthusiasm.

Greenpeace complained that the captain was being used as a "scapegoat" while other key players in the disaster were not in the dock -- including current incumbent Prime Minister Mariano Rajoy, who was deputy prime minister at the time.

The conservative Popular Party government in power had ordered the Prestige out to sea away from the Spanish coast instead of following an emergency plan that called for it to be brought to port where the leaking oil could be confined.

And Rajoy initially downplayed the gravity of the accident, repeatedly describing the black spots that appeared in the sea where the tanker went down as "small threads of clay".

Raquel Monton of Greenpeace Spain said the exact owner of the fuel itself had never been fully determined, adding that the 4.1-billion-euros in damages sought was a "ridiculous figure."

By comparison, BP was forced to pay $20.8 billion to settle government claims for damages stemming from the deadly 2010 Gulf of Mexico oil spill.

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