Police in Dean Park attempted to stop a white VW Golf for a routine breath test around 10:15 p.m. on Sunday night. However, the driver reportedly failed to comply, leading officers to initiate a pursuit.

The chase was brief, as officers soon lost sight of the vehicle.

While searching the area, a marked police car from the Nepean Area Command collided head-on with a Holden sedan on Debrincat Avenue in North St Marys.

The 47-year-old driver of the Holden sustained injuries and was transported to Westmead Hospital, where he is in serious but stable condition.

In the police car, a 25-year-old male constable and a 25-year-old female senior constable received on-site medical attention from paramedics before being taken to Nepean Hospital for further evaluation.

A critical incident investigation into the circumstances of the crash is now under way.

The investigation will also be subject of an independent review.