The incident happened at Gallions Reach Health Centre in Bentham Road just after 8pm yesterday (November 16).
Officers and London Ambulance Service crews attended and found a boy injured.
He was taken to hospital for treatment where he remains in a life-threatening condition.
A 16-year-old boy has been arrested on suspicion of causing injury by dangerous driving, driving without insurance, driving without a license and theft of a motor vehicle.
He remains in custody.
A spokesperson for the Metropolitan Police said: Police were called by the London Ambulance Service at 20:06hrs on Sunday, 16 November after reports of a collision between a car and a pedestrian on Bentham Road, Thamesmead.
“A 17-year-old boy was taken to hospital where he remains in a life-threatening condition.
“A 16-year-old boy has been arrested on suspicion of causing injury by dangerous driving, driving without insurance, driving without a license and theft of a motor vehicle.
“He remains in custody.
“Enquiries continue. If you saw anything or have information that could help police, please call 101 quoting CAD 6506/16Nov.”
