The WA Police Union says a fleet of about 30 open cage-style vehicles used to transport prisoners in regional areas are unsuitable and need to be upgraded.

Union safety officer Dave Lampard said he had raised concerns about the vehicles, which were used in country towns, about two years ago.

"WA Police are often required to escort juvenile and adult remand prisoners within certain areas of regional WA," Mr Lampard said. "These escorts often place undue stress and anxiety on our members due to the unsuitability of the vehicles for this use. It is ironic that most older style cells have been banned from use in police stations, yet prisoners are detained in a far more vulnerable environment (in unsuitable vehicles)."

Concerns about prisoner transport have intensified after an inquest into the death of an Aboriginal elder in a Department of Corrective Services van being driven from Laverton to Kalgoorlie. He died of heatstroke.

Coroner Alastair Hope said the man's treatment was disgraceful and the vehicles used by contractor GSL, which is now G4S, were not fit to transport people.

The death led to the two G4S drivers being sacked this week and seven unsuitable vehicles being taken off the roads. It also prompted a rally in Perth today.

Police Commissioner Karl O'Callaghan said the incident highlighted the need to upgrade police vehicles or transfer all transport services to a contractor.

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