A 60-year-old man has been airlifted to hospital with serious injuries after his Austin Maestro collided with a police car.
Dorset Police have informed the Police Complaints Authority about the accident, which also left two police officers with minor injuries.
On Tuesday afternoon the vehicle driven by the man from Bournemouth, Dorset, was in collision with a Volvo police car on the B3081 near Cranborne, closing the road for almost eight hours.
He was cut free from the car by firefighters and taken to the Dorset County Hospital in Dorchester by air ambulance, suffering from life-threatening injuries.
The man, who works as a painter and decorator, is now in a stable but critical condition in the intensive care unit.
His Maestro was travelling east and the police car, containing two officers based at Ferndown, was travelling west.
The two officers suffered minor injuries and were treated at Poole Hospital and later released.
Chief Superintendent David Burgess, of Dorset Police, said: "Our thoughts are with the driver of the Austin Maestro and his family, together with the two police officers involved in the collision.
"This road traffic collision is being fully investigated and Dorset Police
will be informing the Police Complaints Authority of the circumstances surrounding this incident."
Police are urging any witnesses to the crash to come forward.