Western Australia's Child and Adolescent Health Service (CAHS) has rejected claims that its mental health Acute Response Team (ART) is being cut back.

The ART provides a phone advisory service for mental health issues, as well as urgent assessments for children and young people in hospitals and in the community.

This includes patients referred from Princess Margaret Hospital's (PMH) emergency department.

While the team is based at PMH's premises, it is not funded by the hospital.

It has been proposed that the ART and the Acute Community Intervention Team, which provides short-term support, become part of the CAHS community team.

This means the services could be primarily based in clinics around Perth.

A spokesperson for CAHS said that decision was "based on feedback from consumers and families about the importance of being able to access services close to home".

The spokesperson said the services were "safe, and will be funded", but the precise amount for the next financial year was still being negotiated between the Department of Health and the Mental Health Commission.

The details of the new model will be finalised in the coming weeks.

The 24-hour helpline will be available during the transition - as well as in the new model - although it is yet to be decided where the phone service will be based in the future.

Service has been vital: Opposition

WA Opposition's mental health spokesman Stephen Dawson said he had heard concerns the 24-hour operation was under threat.

Mr Dawson said the phone service had experienced strong demand.

"I hear from families that I've dealt with that this service has been invaluable," he said.

"Because it's available 24 hours a day, it's been able to answer the questions that people have needed at the times that they've needed them.

"You know it's simply not the case that mental illness arises between nine and five."

"It happens or arises in the middle of the night, so that's why this service has been vital.

"Over the last 12 months, 159 young people were discharged from adult beds in adult hospitals because, simply, the beds weren't available, the children's beds weren't available.

"We know more services are needed, not less."