French prosecutors have launched criminal proceedings against those responsible for the tanker disaster which is now threatening the French coast.

Small lumps of oil from the tanker, the Prestige, have already begun to land on the country's south-western shore. The slick has already devastated beaches in north-west Spain.

So far the oil is washing ashore in small lumps

French officials say about 100 larger slicks are on their way, driven by strong winds.

"The pollution now affecting the French coastline obliges us to proceed with a formal investigation to seek out and punish those responsible for this ecological catastrophe," said a spokesman for French President Jacques Chirac.

The Liberian-registered Prestige began leaking on 13 November and sank after breaking in half six days later, 130 nautical miles west of Spain.

'Messenger' birds

Part of its cargo of 77,000 tons of fuel oil contaminated Spain's richest fishing grounds and spilt onto the north-west Galician coastline.

The French president's spokesman said prosecutors would establish whether "those on board, or the owner, or the operator, or their representatives" were to be held legally responsible.

Police, firefighters and troops began a clean-up operation on Thursday, after confirmation on Wednesday that lumps of oil washed up on beaches over the last few days came from the Prestige.

They were sent into operation in the Landes region, between Biarritz and Bordeaux, which has some of France's most popular surfing beaches.

The Society for the Protection of Birds said on Thursday that 170 seabirds had already been found dead, describing them as "messengers of major oil pollution off the coast".

About 100 injured birds have been recovered and are receiving treatment.

Beach closures

"We know that there is a concentration of oil slicks from... Bordeaux to Santander in Spain," Ecology Minister Roselyne Bachelot told the Le Parisien newspaper.

Spain has put thousands of troops on clean-up duty

"If the weather continues as we expect, then these slicks could wash up in the estuary of the Gironde around 5 January," she added.

She described the slicks as a "sword of Damocles" that would hang over France for a long time.

Experts have suggested it could take months for the oil to wash ashore, with dire effects for the local tourist industry.

Local authorities in the Gironde region called on Thursday for some beaches to be closed for the duration of the cleanup.

Weather difficulties

High winds have prevented teams of fishermen going to sea to attempt to scoop up the slicks in their fine-mesh nets.

Some of the tanker's holes have been sealed

They have also hampered attempts to track the slicks from the air.

The Prestige is estimated to have spilled about a quarter of its cargo. Some of the rest is slowly leaking from the damaged hull.

A French mini-submarine has been plugging cracks in the tanker to prevent further leakage, but it too has been out of action for more than a week because of bad weather.

For France, the latest oil leak revives painful memories of the oil spilt in 1999 by the tanker Erika on the Brittany coast, causing some $860m of damage.

The Prestige crisis has already cost Spain $250m.

Westerly winds driving the oil towards France are forecast to continue.