A man who allegedly attacked another man outside a Christchurch carwash is set to appear in court today

The victim was left critically injured after being stabbed by the driver of another car at the intersection of Clarence Street and Blenheim Road just after 5.30 on Thursday afternoon.

The two vehicles were stopped at red lights at the time - the victim was in the backseat of a car with three other adults.

A 26-year-old is charged with wounding with intent to cause grievous bodily harm.

Police don't believe those involved knew each other, but haven't confirmed what caused the altercation.