Ant McPartlin has been arrested on suspicion of drink-driving, according to reports.
The TV star, 42, is said to have been involved in a collision with two other cars while he was driving his Mini in Richmond, West London, on Sunday afternoon.
He failed a roadside breathalyser test and was arrested.
Police said a child passenger from one of the cars was taken to hospital to be checked as a precaution.
A Metropolitan Police spokesperson said: "Police in Richmond were called to Lower Richmond Road, SW14 at 15:59hrs on Sunday, 18 March following reports of a road traffic collision involving three vehicles.
"Officers, London Ambulance Service and London Fire Brigade attended.
"A number of individuals were treated at the scene for minor injuries only.
"A child passenger from one of the cars has been taken to hospital for a check up as a precaution.
"A 42-year-old man was arrested at the scene on suspicion of drink-driving after failing a roadside breathalyser test.
"He has been taken to a south London police station for questioning. Enquiries continue. Roads are expected to reopen shortly."
McPartlin entered rehab last year after struggling with an addiction to painkillers.