The man was working for a subcontractor on the Cornwall Energy Recovery Centre project being developed by SITA UK, near to the village of St Dennis, near St Austell.

He was taken by air ambulance to Derriford Hospital in Plymouth, after been found “breathing but unconscious at the scene” on Tuesday morning.

A South Western Ambulance Service spokesman said the man had fallen 10m and suffered serious head and arm injuries.

A SITA UK spokesman said: “Regrettably, at approximately 10am a serious incident occurred on the construction site of the Cornwall Energy Recovery Centre.

“A construction worker employed by a subcontractor of main contractor VINCI sustained injuries following a fall from height.”

He added: “An internal investigation is now underway to establish the cause of the incident by the main contractor VINCI Environment UK Ltd. The majority of work at height remains suspended.”