There are calls to change prison transportation systems after a young woman was transported from prison to a mental health facility naked while she was experiencing menstrual bleeding.

The Indigenous woman was in severe distress when she was transported from Bandyup Women's Prison to a mental health hospital in Western Australia — and was in the back of a van handcuffed, naked and bleeding from her period for 40 minutes.

The incident, which happened in August of last year, is being investigated by the Office of the Inspector of Custodial Services.

Professor Neil Morgan, inspector of custodial services in WA, said the incident raised serious concerns about the prison system.

"I am carrying out an investigation into what happened, and more generally an investigation into whether this was a one-off issue or whether it is a more systemic issue," Professor Morgan said.

"It's a basic human right. Basically it is about the decent treatment of human beings in custody and it is about how we in society behave towards to people in prison."

He called for better treatment of people in prisons and said there needed to be more services available for offenders with acute mental health issues.

"Many, many people in prison have a significant mental health issue and we need to do better as a society to deal with that. This is one example that our prisons are housing people who really are so unwell that they belong in a mental health facility — not in a prison," he said.

Professor Morgan said there was only one secure mental health facility for prisoners with complex mental health issues — but it only had 32 beds.

"It's not very much, and when you think since our prison population has tripled during that time [since 1993], then it is well overdue for the Government to invest money into forensic mental health facilities," he said.

Prison transport 'not simply a taxi service'

Concerns are also being raised about the contracting of prisoner transportation — with often untrained people dealing with complex needs of prisons.

"I think we need to look at how we best transport people with complex needs, but it's not really a question of whether it is a private contractor or somebody else," Professor Morgan said.

"People who work in the prisons in the public sector are also not terribly equipped to handle a situation of this sort — a very unwell and distressed young woman.

The issue of appropriate prison transport remains contentious in Western Australia following high-profile incidents such as the death of an Indigenous man known for cultural reasons as Mr Ward, who "cooked to death" in the back of a prison van operated by contractors G4S while being transported in 44-degree-Celsius heat a decade ago.

Mr Ward was being transported 360 kilometres from Laverton to Kalgoorlie in 44-degree heat. ( ABC News )

During a coronial investigation into the incident, Perth barrister Linda Black represented G4S guard Graham Powell, and who was later found by a court to have contributed to Mr Ward's death.

Ms Black said this latest incident revealed some of the community's most "vulnerable members" were being transported by outsourced companies who have drivers who were not necessarily trained or experienced.

"[The prisoners are] people who have mental health issues, who may have drug issues, violence issues — a whole multitude of problems," Ms Black said.

"We are having companies who are outsourced by our Government, by corrective services, engaged in transporting prisoners.

"It's not simply a matter of them providing a taxi service — there are serious duty of care and welfare issues."

Ms Black said the case was disturbing.

"That [the death of Mr Ward] was the last time I can recall the Department of Corrective Services really coming under fire," she said.

"Now the problem here is that none of us know what happened here, and the full circumstances."

The State Government said in a statement that it was informed of the incident shortly after it happened and the Minister for Corrective Services supported the issue being referred to the Inspector of Custodial Services.

The investigation is now examining the wider issue of prisoner transfers.

Transportation contractor Broadspectrum has been contacted for comment.