The environment group Greenpeace yesterday occupied Rockall, an uninhabited rock outcrop 290 miles west of the Scottish mainland, in protest at oil exploration in the Atlantic.

Three activists were landed by helicopter on the 100ft high rock, Britain's most-distant island, and said they planned to stay there indefinitely in a solar survival capsule held down with steel pins.

A spokesman said: "We dispute the moral and political right of the UK to develop this ocean for more oil. We have asked the UK Government to stop oil exploration in the Atlantic Frontier region and when they do they can have their rock back."

However, the occupation was described by the United Kingdom Offshore Operators' Association as a publicity stunt which diverted attention from real issues. BP - recently issued with an exploration licence in partnership with Shell and Statoil in the Atlantic Frontier area around Rockall - said the new oilfields west of Shetland were replacing North Sea production, and not adding to it.

The tiny island, which is regularly swept by high seas, gives Britain territorial rights over a large area of the ocean seabed. Seabirds are its only regular visitors, although it is not attractive enough for them to breed there. Despite its size, it has been the subject of territorial disputes involving Ireland, Iceland and Denmark.

Britain's claim to the island was consolidated in 1955 when a group of Royal Marines landed on Rockall and raised a Union flag.

Greenpeace named the three members of the occupying force as Al, 32, from Newhaven, Sussex, Peter, 40, an Australian, and Meike, 31, a German woman.

Matthew Spencer, an activist on the converted Dutch tug Greenpeace, which is standing by, said carbon dioxide caused by the burning of oil was causing climate change, and the world could not support the burning of the oil reserves already discovered. "So why should oil companies destroy a beautiful wilderness area, which is a motorway for whales, to find more?" he added.

Rockall's last human resident was Tom McLean, an adventurer who runs an outdoor centre at Loch Nevis, in the West Highlands. He spent 40 days there in 1985, living in a coffin-sized box bolted to the rock to raise money for charity. Mr McLean said yesterday: "It is completely vertical on one side and rounded and near-vertical on the other. I can't see any sense in what they are doing. I suppose they will sit there and the oilmen will just carry on." Greenpeace claims that by issuing licences for exploration, the Government has ignored key EU directives over protection of cold water coral which supports 800 species of marine organisms.