It's been revealed a back seat passenger has been a victim of a stabbing in Christchurch

A man's in a critical condition after being attacked by a driver at the intersection of Clarence Street and Blenheim Road, just after 5.30 yesterday afternoon.

The alleged attacker was on his own in the car, and victim was a rear passenger in another car of four adults.

The vehicles were stopped at red lights when the incident unfolded - the man then fled north on Clarence Street towards Riccarton Road.

Police would like to speak to anyone who witnessed this incident or has footage of it.