Plans to expand a quarry near an ancient monument have been likened to 'dropping Stonehenge into the River Avon'.

The comment comes from archaeologists backing protestors fighting the expansion of Nosterfield Quarry, close to Thornborough Henges, near Bedale, North Yorkshire.

George Lambrick, director of the Council for British Archaeology, is one of several senior archaeologists who have spoken out against the plans by owners Tarmac Northern.

He said: "The proposals are contrary to national and local policy."

"The application is incomplete, non-compliant with regulatory requirements, and granting consent would set unacceptable precedents."

The site is said to contain the greatest concentration of late Neolithic and early Bronze Age henges - or circular monuments - in the country.

It is thought the henges may have been the most important sacred site in Britain 5,000 years ago.

Other experts backing campaign group Heritage Action in their fight against the extension include Peter Addyman, of the Yorkshire Archaeological Society.

He said: "This area is part of an extensive area of archaeological importance and potential, the destruction of which, even with archaeological recording and survey, is not in the local, regional or national interest."

While archaeologist and Stonehenge expert Aubrey Burl likened Tarmac's plans to dropping the Wiltshire stone circle into the River Avon. George Chaplin, Thornborough Henges campaign co-ordinator for Heritage Action, said: "The archaeology world is not well known for either speaking out or co-ordinating activities, but now it seems that a strong consensus against the quarrying at Thornborough is building.

"The signs are that Britain is waking up to this savage threat to our heritage."

Heritage Action has already delivered nearly 1,000 letters objecting to the expansion to North Yorkshire County Council."

The group is also holding talks to persuade the public to back its campaign.

However, Tarmac Northern has defended its proposal.

Bob Nicholson, estate manager for Yorkshire, said the extension to the quarry would be several hundred metres from the henges.

He said: "Tarmac does care about archaeology."

"That's why we take so much time and effort to find out what we can - every time we go into an area it's almost like a full archaeological dig takes place."

The planning application will be considered by councillors next month.