An investigation into the suicide deaths of five St John Ambulance paramedics and volunteers found flaws in how staff are managed.

Western Australia's ambulance service has been told to improve the way it treats paramedics in a report into a spate of suicides at the organisation.

The report by WA's chief psychiatrist Nathan Gibson into the suicides of five St John Ambulance paramedics and volunteers recommended the organisation improve its conflict resolution and performance management processes, amid accusations of workplace bullying.

The deaths occurred over the 16 months to March last year.

Dr Gibson did not say whether or not there was a culture of bullying at the organisation contributing to the deaths because that was not within his scope.

St John chief executive Tony Ahern rejected any suggestion of a bullying culture but said it was an issue throughout Australian workplaces, including his.

However James Vaughan, the brother of one of the dead paramedics Marcia Vaughan, said on Wednesday that his sister suffered from a build-up of post-traumatic stress disorder and bullying, and felt under-supported by management while working in the remote Goldfields-Esperance region.

A workplace lawyer also told ABC Radio she had represented several paramedics and that bullying was systemic there.

Dr Gibson said no one specific issue contributed to the deaths.

It was a combination of the stress and trauma of being "first responders" to emergencies - something police and firefighters also tackled - along with St John-specific workplace and organisation factors, and social and individual factors.

Paramedics were proud of their jobs but it was challenging for emergency services across Australia, not just WA, and first responders dealt with extremely traumatic experiences and different people responded in different ways, he said.

He listed seven recommendations for St John to improve how it operates, which the health department will follow up.

Health Minister Kim Hames defended the organisation, saying the century-old service had a very good reputation serving West Australians and he had seen no evidence of cultural issues there.

However he wanted to see a separate report St John had commissioned that was broader in its scope examining the organisation, but conceded he could not force its release.

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