Officers believe the man was deliberately targeted because the vehicle did not stop at the scene.
Roads in the area are still closed, and a crime scene has been set up.
A Met spokesperson told the Havering Daily:
Police were called to reports of a man injured after being hit by a car in Latimer Drive, Hornchurch, at approximately 12,45am on Saturday, 25 June.
Officers and the London Ambulance Service responded, and the man, who was in his twenties, was taken to hospital for treatment of his injuries; he is still in critical condition.
“His next of kin has been notified.”
“The car did not stop at the scene, and officers believe it was deliberately driven at the man at this point.”
“There have been no arrests; investigations into the circumstances continue.”
“Officers are maintaining a presence in the area and providing reassurance to the local community.”
Anyone with information that could help the investigation is asked to call 101 or tweet @MetCC with the hashtag CAD265/25June.
You can also call the independent charity Crimestoppers anonymously at 0800 555 111.