The sunken tanker Prestige may continue to send oil oozing into the Atlantic until 2006, Spanish experts have revealed.

It would take between a minimum of five and a maximum of 39 months to empty the tanks Emilio Lora-Tamayo Head of commission

A Dutch firm is preparing an ambitious plan to pump the remaining oil to the surface, in an operation which would be among the most complex salvage bids ever attempted.

The heavy fuel oil on board the wrecked vessel is currently leaking from 15 cracks in the hull at the rate of up to 125 metric tons a day.

The revelation of a prolonged, slow loss of the 60,000 tons on board confirms the worst fears of the Spanish Government, which had hoped that the cold temperatures and high pressure would solidify the oil.

The tanker is lying in 3,500 metres of water

But the head of the Spanish scientific committee set up to analyse information on the tanker says a slow leak is in prospect.

"It would take between a minimum of five and a maximum of 39 months to empty the tanks," said Emilio Lora-Tamayo.

It could mean the leak continuing until March 2006, he said.

"When it comes to the flow, estimates are that there are some 80 tons per day leaking from the bow and around 45 tons from the stern. We are talking about 120 to 125 tons per day," Spanish Deputy Prime Minister Mariano Rajoy told reporters in the port city of La Coruna.

Prestige facts

11,200 tons of oil scooped from sea by special vessels 1,600 tons recovered by fishermen Nearly 200 beaches hit 7,000 soldiers and volunteers helping clean up Prestige lying in 3.5 km (2.2 miles) of water 125 tons (33,000 gallons)

The Dutch firm Smit, which was involved in plans to salvage the nuclear submarine Kursk, revealed on Wednesday that it was preparing a detailed salvage proposal, which would cost an estimated 50 million euros.

The firm has yet to release full details of its plan, but reports say Smit is looking at ways of sealing the leaks and pumping the remaining cargo to the surface.

The proposal is expected to be formally presented to the affected parties within days, spokesman Lars Walder told BBC News Online.

Information about the state of the wreck is being provided by the French mini-submarine Nautile, which has located the two sections of the wreck on the Atlantic seabed.

The two parts are lying around four kilometres (two miles) apart, around 240 km (130 nautical miles) off the Galician coast.

The ship haemorrhaged an estimated 15,000 tons of its cargo before spectacularly breaking in two and sinking in November.

Thousands of birds have been caught up in the oil

The slicks have contaminated dozens of beaches along the Galician coast, devastating the fishing and seafood industries, threatening the tourist trade and taking a heavy toll on wildlife.

News of the continuing leaks has focused fresh attention on the government's handling of the crisis.

The Prestige was towed out to sea before it sank, after both Spain and Portugal refused to allow it into port.

The decision was taken in an attempt to minimise damage along the coast.

But the effect has been to place the wreck in water so deep that the task of salvaging the oil or stopping the leaks has been made all but impossible, some experts say.

The water is so deep - 3,500 metres (12,000 feet) - that it takes a day for the escaped oil to reach the surface.

Public anger

The rate of flow is varying, Mr Rajoy said, speeding up when the water is warmer, and slowing down when it is cooler.

The Nautile is due to dive again to the wreck on Wednesday to check the latest situation.

Amid growing public anger at the government's handling of the crisis, Prime Minister Jose Maria Aznar admitted on Monday that mistakes may have been made.

Much of the oil has reached shore, but large slicks are still at sea.

The biggest measures 57 km by 18 km (35 miles by 11 miles), and contains around 30 tons of oil.

France and Portugal remain on alert, but so far no oil has come ashore on their coasts.