The French mini-submarine Nautile is to try to stem the steady leakage from the wreck of the sunken oil tanker Prestige that has already polluted much of Spain's north-western coastline.

The Nautile team will attempt an experimental placement of stoppers on certain leaks to see if we can tackle the problem this way Spanish Deputy PM Mario Rajoy

The Nautile is also to gauge the temperature of the tanker's leaking oil, its rate of leakage and obtain a sample, said Spain's Deputy Prime Minister Mario Rajoy.

The Nautile has already made five dives to where the sunken tanker lies - 3,500 metres (11,500 feet) deep in the sea - leaking more than 100 metric tons of fuel oil a day from several cracks in its hull.

Dutch shipping and salvage firm Smit International - which helped raise Russia's Kursk submarine - has formally submitted a proposal to the Spanish Government and the European Union officials to salvage oil from the wreck.

Smit, which in charge of salvaging Prestige before it sank, said the operation - to pump the oil back to the surface - would cost nearly 50m euros and take several months to complete.

It said it was confident technology it had used before could work.

A third wave of slicks is on its way to the north-western Galician coastline, amid concerns about the risk to local deep sealift-rich estuaries, known as "rias".

The rias produce most of the region's annual 300,000 tons of mussels - Europe's largest production.

Anger

There is mounting anger in north-western Spain against the government's handling of the Prestige disaster.

In the largest protest so far, about 150,000 people took to the streets in the fishing port of Vigo on Wednesday, calling for government resignations and for laws to ensure no such disaster happens again.

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) leaking daily

Anger also mounted on Thursday in Galicia's regional parliament, as opposition legislators tried to censure its ruling conservative leaders for their management of the disaster.

Experts have said the Prestige may continue to send oil oozing into the Atlantic until 2006.

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.