GREENPEACE must get off Rockall within three weeks - or apply for planning permission to live there.

Planners at Western Isles Council yesterday decided on the get-tough policy after the environmental activists had proclaimed the rock as a new sovereign state, called Waveland, on Sunday.

Greenpeace reacted last night by greeting the Western Isles as a neighbouring state, and invited its officials to a site visit.

Three activists have been living on the windswept 70ft outcrop in a yellow watertight capsule since the middle of last week. They hope the declaration of the new state will be a hurdle to the development of oil and gas fields to the west of the islands.

Officials at the council's headquarters in Stornoway yesterday admitted they had no idea how to enforce planning laws if the new occupants of Rockall, almost 300 miles west of the Hebrides, did not comply to their warning.

Council policy adviser John Clark said: "We have a legal duty to enforce planning regulations in all areas where we have jurisdiction. Rockall, in fact, comes under the Obbe ward in South Harris.

"Greenpeace has 28 days from the date its people moved in to make the application for retrospective planning permission."

Their hardline approach could even see attempts to collect council tax from the new residents of Obbe ward. The council is unsure of the value of the Greenpeace capsule, but reckons - for the purpose of assesssing it for council tax - it may come into Band A, the least expensive category.

The islands' authority, they stressed, is not being needlessly unfriendly to Greenpeace. "We are just doing what we are legally bound to do," said Mr Clark.

Meanwhile, Greenpeace rejected the Western Isles Council's stance, saying it did not recognise the council's jurisdiction. Spokeswoman Sue Cooper said: "We do not necessarily accept any nation has any sort of development rights, and hence planning controls over Rockall.

"If the council wants to come on a site visit, we would be happy to arrange it, and welcome them to the first capital of the Global State of Waveland."