A proposal from Brussels would modify the traditional dictionary definition of a piece of land surrounded by water, and could mean that many of the UK's most famous islands would become legally landlocked.

Under the EU plan, an island is not an island if it has fewer than 50 permanent residents, is attached to the mainland by a rigid structure, is less than 1km from the mainland, or is home to the capital of an EU state.

The proposal, part of a revamp of the European regional development fund, means that the island of Skye, known for centuries as the Misty Isle, would need a new moniker, because it is joined to the mainland by the Skye Bridge.

The island of Bute, which can only be reached by ferry, would also lose its status, because it lies 400 metres from the west coast.

Other non-islands would include Rhum, Muck, St Kilda, and the Isle of Anglesey.

The bemused residents of Muck recently suggested that they could be reclassified as a shipping hazard. Officials say the proposals could have serious implications if they are adopted in three years' time, with many of the affected non-islands potentially losing millions in aid.

"It is this kind of crass, idiotic stuff that comes out of Europe that spoils the positive effects of European membership," said Ian Gillies of the Scottish Islands Network.

"This is all steeped in the reorganisation of Europe in 2006. What the European Union community is trying to do is cut down on the amount of aid they may have to provide to islands. At the moment, many of the islands off the west coast of Scotland are beneficiaries of ERDF funding."

Drew Miller, a local councillor who runs the post office in Portree on Skye, said that the inhabitants would always consider themselves islanders, no matter what Europe said. "We think it is bureaucracy gone mad," he said.

EU officials are due in Scotland this summer, and Mr Gillies intends to show them the difference between the mainland and an island.

"People are dumbfounded that anyone could suggest these are not islands," he said. "Just try and walk there."