GREENPEACE activists have set up home on Rockall, the barren rocky stack 289 miles off northwest Scotland, and say they wi11 not leave until the Government promises to stop oil exploration in the Atlantic.

Two men and a woman arrived by helicopter on Tuesday night and promised to stay indefinitely in a 12ft by 6ft survival capsule. which was clamped to a ledge with steel pins. "We have asked the Government to stop oil exploration in the Atlantic Frontier region and when they do they san have thier rock back," a Greenpeace spokesman said.

The Govemment, however, was unconcerned, and rather puzzled, by the protest. A Foreign Office spokesman said: "Rockall is part of the UK. My understanding is that people are free to move around the UK as they wish. They can stay there as long as they like." The Department of Trade and Industry was similarly unruffled. "Anyone can stay on Rockall - if they really want to," a spokesman said.

The adventurer Tom McClean, who spent 40 days there in 1985 to raise money for charity, said: "I can't see any sense in what they are doing. I suppose they will sit there and the oilmen will just carry on. But good luck to them."

Mr McClean, who has rowed the Atlantic, said that leisure activities were limited because the rock faces made it difficult to walk about and there was a danger of being washed away by high seas. The 65ft-high rock is regularly lashed by 90ft storm waves. But Mr McClean said it was pleasant to chat to fishermen by radio.

The Greenpeace trio are Al, 32, from Newhaven, Sussex, Peter, 40, from Australia, and Meike, 31, a German woman. No surnames have been given. Al and Meike are veterans of the successful Greenpeace protest against the dumping of the Brent Spar oil platform in the Atlantic in 1995. The MV Greenpeace will stay in the area to deliver supplies. It is captained by John Castle, veteran of the Brent Spar.

The survival capsule is equipped with solar- and wind-powered computing and communications equipment. But lavatory facilities will be distinctly low-tech: "bucket and chuck it", a Greenpeace spokesman explained.

The aim of the protest is to draw attention to global warming caused by fossil fuels. Greenpeace claims that more than 30 oil companies are prospecting in the Atlantic Frontier area despite scientific evidence that the burning of existing oil supplies will have a grave effect on the climate. Al said: "No one has the right to unleash this oil on to our threatened climate."

The oil industry dismissed the protest for "trivialising the issues" surrounding the need for gradual change to renewable energy sources. Andrew Searle, of the UK Offshore Operators Association, said that the protesters were making unrealistic demands that the fossil fuel industry be "shut down tomorrow". He said that would jeopardise 300,000 jobs in the UK and was, in effect, asking people to move back to the Stone Age".

Greenpeace has threatened to take the Government to the High Court over its alleged failure to apply European law to protect cold-water coral in the Atlantic. It wants licences for oil and gas exploration suspended.

BP and Shell are expected to start production at the Foinaven oilfield, 100 miles west of Shetland, later this year. The £550 million development, the first in the Atlantic Frontier, will produce up to 95,000 barrels of oil a day. A BP spokesman said the Atlantic oil would replace declining production in the North Sea.