The West Australian police service has been heavily criticised in a Coroner's report into the death of an Aboriginal teenager.

In a scathing report, the Coroner Alastair Hope says the police service must take much of the responsibility for the death of the 17-year-old, who was placed in the back of a police utility after being arrested for traffic offences last year.

The boy died after falling from the back of the vehicle near Fitzroy Crossing.

The arresting officers drove for three kilometres before realising the back door of the van was swinging open and the boy was missing.

Mr Hope says defects associated with the locking mechanism of the security cage had been identified shortly before the incident, but no action had been taken by the service.

He has called for a review of all security vans in the police fleet.