The helicopters from Royal Naval Air Station Culdrose in Cornwall were dispatched to the vessel Erika, registered in Malta, which became caught in 60mph winds and 20ft waves north of the Bay of Biscay.
Everyone on board the tanker, which was carrying 26,000 tons of diesel oil from France to Italy, was winched to safety and taken ashore. French officials said that up to 5,000 tons of fuel had leaked into the ocean, but it would be two days before oil would start washing up on the coast.
Tony Juniper, policy director of Friends of the Earth, said: "This incident once more proves that a great deal more needs to be done to prevent pollution of this kind." The authorities should insist on higher standards rather than "hoping that stormy weather will blow the problem away," he added.
The British Sea Kings were called to the scene, about 70 miles south of Brest, at about 7.30am because the French feared they did not have enough aircraft for the rescue.
Lieutenant Fraser Hunt, one of the helicopter pilots, helped to search for crew as French helicopters winched them to safety. "It was very rough," he said. "The bow of the tanker was in one place and the superstructure was about a quarter of a mile away. The 26 people on board were all recovered." After the rescue, the naval helicopters returned.
Yves Merle, a Brest Port Authority captain, said that a tug, the Abeille- Flandre, pulled one half of the vessel further from the coast into deep waters. The other severed section was floating vertically and would not be moved until the weather has cleared up, he said.
A team will siphon oil out of the tanker on to another boat if the weather clears. "Everything depends on the sea conditions, which today are still very bad," said Mr Merle.
There were conflicting views as to the danger presented by the type of fuel oil involved. Christophe Rousseau, an official at the marine pollution centre in Brest, said there was a chance that the waves would "pulverise" the oil that had leaked, but another specialist said the thickness of the oil was a worry.
Admiral Yves Naquet-Radiguet, maritime prefect for France's Atlantic coast, said the owner of Erika, which had been heading for Italy from the northern French port of Dunkirk, was exploring the possibility of transferring the oil still aboard to another vessel.
Britanny was hit by an ecological disaster in March 1978 when the Amoco Cadiz supertanker foundered on the Finistere coast, spilling 280,000 tons of crude oil.