An air ambulance landed at the Riverside Field site in Hebburn to fly the injured man to Royal Victoria Infirmary in Newcastle.
According to an eye witness report a JCB digger reversed into worker after the machine’s throttle is believed to have jammed.
Jim Entwistle, spokesman for the Great North Air Ambulance Service, told local news website Chronical Live said: “We were called shortly before 11.30am to a construction site in Hebburn.
“It was an industrial incident which left a male, in his early 40s, with serious chest and abdominal injuries. We worked alongside the North East Ambulance Service at the scene.
“We treated him at the scene and took him by air ambulance to the Royal Victoria Infirmary in Newcastle. The journey took four minutes. He was critical but stable.”