Energy firms taking part in a North Sea boom for offshore wind farms will have to watch out for remains of Stone Age villages submerged for thousands of years, an expert said yesterday.

A region dubbed "Doggerland" connected Britain to mainland Europe across what is now the southern North Sea until about 8,000 years ago, when seas rose after the last Ice Age.

It is now the site of a planned vast expansion of offshore wind power by 2020 to help combat climate change.

"We've begun to think about how we'd tackle any archaeological finds," Adrian Fox, supply chain manager of the Crown Estate which leases land off Britain, told Reuters during a conference in Oslo about offshore wind.

He said planners were trying to consider every challenge of offshore wind farming - from upgrading port capacity to finding more specialised vessels to help install the turbines.

Discoveries of ancient Roman sites in London have sometimes held up construction projects for years. "We want to decide how to treat (archaeology) reasonably so we don't hold up projects for ever," Mr Fox said.

Over the decades, North Sea trawlers have netted artifacts including a harpoon made of antler, and bones of mammoths and reindeer. Archaeologists' studies suggest Doggerland would have been a fertile region before it was swamped by melting ice.

Britain is leading a drive to exploit wind energy in the North Sea with licences for a capacity of about 32 gigawatts, part of a push to get 20 per cent of energy from renewable sources by 2020.

The biggest will be on the Dogger Bank, where waters are between 18 metres and 63 metres deep, by the Forewind Consortium of Scottish and Southern Energy, RWE npower, Statoil and Statkraft.

Julian Brown, director of the British consultancy BVG Associates, said that turbine manufacturers around the world were showing interest in the North Sea.

"We have a list of 13 turbine manufacturers who'd like a role in the UK offshore," he said.

The companies include Siemens, Vestas, General Electric, China's Sinovel and Goldwind, he said, adding that there would probably not be space for all of them.

Forecasts for the growth of offshore wind farms in Europe imply investments of between $135 and 200 billion over the next decade, said Erlend Broli of Norway's Statkraft. All experts said costs had to come down to make offshore wind more competitive. The conference was organised by Norway's INTPOW group, which promotes renewable energies.