THE controversial Mynydd y Betws windfarm seemingly faces question marks over its future after experts claimed to have discovered a 5,000-year-old Stone Age monument “almost as significant as Stonehenge” on the site.

The 500-metre Neolithic stone row– believed to date from around 3,000BC – has been described as having “national, possibly even international, significance”.

The discovery – if confirmed – also raises questions over the planning permissions granted to the developers, Irish power firm ESB.

The Guardian has previously reported how ESB spokesman John O’Donohue said that archaeological surveys of the site failed to unearth anything of significance.

“We didn’t find anything, but we would have to stop if something was discovered,” he told Betws community councillors after the possible presence of sites of religious and archaeological interest was first raised by Cllr Maldwyn John in October.

Contractors at the site have fenced off the find, but opponents of the scheme say the discovery – part of which has already been destroyed during the windfarm’s construction – is one among many.

“The whole mountain is covered with archaeological artefacts,” said Geoff Moore of campaign group Communities Acting Together. “We have shown the find to two wellrespected experts and they were astounded to find such a fine example of something which is very, very rare in Wales. What concerns me most is that if it takes lay-people like us to spot something that is so enormous and important to our history, why was it not seen during the original survey? Does this mean that the decision to approve the plans was based on incorrect or flawed information?”

Freelance archaeologist Helen Gerrard described the find as “tremendously important”. “There is only one of its type in Britain which has even been partially excavated,” she said.

“This could be almost as important as Stonehenge.”

A spokesman for Cambrian Renewable Energy Limited, the company building the turbines, said the firm was consulting its archaeologists and Carmarthenshire County Council. “Further statements will be issued when more information becomes available,” he said.