Police in Hackney were called to Kingsland Road junction with Ridley Road, E8 at 23:27hrs on Saturday 3 May to reports of a road traffic collision between an unmarked police car and a 22 year old female pedestrian.
The injured pedestrian was taken to a central London hospital where she remains in a critical condition.
The police vehicle, on blues and twos, was attending an incident prior to the collision. No arrests have been made.
Enquires are continuing and this incident has been referred to the IPCC for consideration.
Anyone who witnessed the incident or has information that they believe could assist the investigation should call the Serious Collision Investigation Unit at Chadwell Heath Traffic Garage on 020 597 4874. To remain anonymous call Crimestoppers on 0800 555 111.