Opponents say the plans threaten the 'Stonehenge of the North'

Construction firm Tarmac wants to extend its activities close to Thornborough Henges, near Ripon.

The firm and English Heritage is still collecting archaeological information, delaying the planning permission process.

The scheme has attracted a storm of protest from heritage enthusiasts.

No threat

A spokesman for the Heritage Action group said that amongst those opposing the scheme was archaeologist Aubrey Burl who likened the plans to dropping Stonehenge into the River Avon.

But a spokeswoman for Tarmac said the site was not under threat and added there were no plans to dig up or destroy the henges.

She said the company would work alongside archaeological experts.

The site has the greatest concentration of late Neolithic and early Bronze Age sites in the UK.

It also boasts the country's largest quarrying operation on prehistoric land, Nosterfield Quarry, which produces more than 500,000 tonnes of sand and gravel each year.