Police were called at 9.38am on Friday, 1 January to reports of a collision involving a car and a pedestrian at the junction of Plough Lane and Foresters Drive.
Officers attended, along with London Ambulance Service, London’s Air Ambulance and London Fire Brigade.
A 50-year-old man was taken to a south London hospital where he remains in a critical condition. His next of kin have been informed.
The driver fled the scene. Officers from the Met’s Serious Collision Investigation Unit are working to trace the driver.
Detective Sergeant Nick Bale said: “Officers are working round the clock to trace the driver involved and we are confident we know the identity of the driver.
“I would urge that person to contact the police as soon as possible. I would also like to hear from anyone who has information about the collision.
Anyone who can help police is asked to call the Serious Collision Investigation Unit based at Merton Traffic Garage on 0208 543 5157.
Alternatively, call 101 quoting CAD 4138/01Jan.