Priceless archaeological sites located on Teesside and North Yorkshire farmland could be destroyed if intensive agricultural methods are not controlled, experts have warned.
English Heritage chief executive, Dr Simon Thurley, flashed the alert while launching a campaign to get more protection for the sites.
He said an overhaul of the law and the co-operation of farmers was needed to save sites on farmland. Such sites include Bronze Age round barrows near Guisborough, and Claxton moated manor near Hartlepool.
"The increasing power of modern farm machinery means monuments can be swept away in a matter of hours," said Dr Thurley.
He said almost 3,000 sites, which are recognised as nationally important, are on land that is being cultivated - including Hadrian's Wall World Heritage site, Roman towns, Anglo Saxon cemeteries and Neolithic long barrows.
Hadrian's Wall archaeologist Mike Collins hit back, saying that changing from ploughing to pasture on a vulnerable part of the site had "stopped damage and destruction in its tracks. …