A young man is in a critical condition after he was impaled by a fence post in a car crash.

A police spokeswoman said they were called at 4.55pm to an accident where a car collided with a fence on Kidd Rd, Karaka. She believed he had been impaled by a post.

Fire and St John also attended and the man was transported by helicopter to Auckland City Hospital in a critical condition.

The Serious Crash Unit are investigating.