THAMES Valley Police has referred itself to an industry body that investigates complaints against it.
It follows an incident at the border between Reading and Wokingham last week.
There are reports that the force was chasing a driver, but this has not been confirmed.
However, around 10pm on Sunday, June 18, a BMW M4 and Jaguar XF were involved in a collision on the junction of Church Road and Wokingham Road – more commonly known as the Three Tuns Crossroads.
The driver of the Jaguar sustained serious injuries and was taken to hospital.
The junction was closed for several hours to allow police to carry out their investigation.
A spokesperson for Thames Valley Police said: “A 21-year-old man from Reading was arrested on suspicion of dangerous driving, failing to stop, driving a vehicle with a proportion of a controlled drug above the limit and causing serious injury by dangerous driving.
“As a result of the incident, a mandatory referral has been made by Thames Valley Police to the Independent Office for Police Conduct (IOPC).”