Ms Forrest said she was aware of a young person who had been sent to Melbourne for treatment that could not be provided in Tasmania after "languishing" in a secure adult psychiatric unit in Hobart for at least 12 months.

"We have heard ad nauseam from governments, past and present, that we will have an appropriate adolescent acute mental health unit and beds in Tasmania for years," she said.

"We need access, through a memorandum of understanding with Victorian facilities, to appropriate services until these are built and staffed."

Ms Forrest had been told the Community Adolescent Mental Health Service had refused to look after the teenager when she returns.

"Her mental illness problems will not disappear because of her treatment in Melbourne and she will need care when she comes back. What then?" she said.

"If what I have been told is proven to be the case, it is disgraceful and I hope something happens to prevent it.

"Adolescents require specialised care and facilities both in an acute setting and community based."

Ms Forrest said she was also aware of other young people in the North West who needed admission to an appropriate facility.

"There is no suitable facility in Tasmania to care for these young people and the situation is untenable for teenagers and their families," she said.

She said while an adolescent mental health facility was being built in Tasmania, it was long overdue.

"Like other MPs, I have had constituents come to me because they are the parents of young people with very significant and serious mental illness who require admission to a child and adolescent mental health facility," Ms Forrest said.

"We are building one, but it is not staffed yet, and I understand it is not necessarily funded yet. Until we have that, we need to be sure we provide adequate support facilities and care for these young people.

"We need to be sure, if we do not have these facilities in the state, that we provide access to these facilities in Melbourne."

Ms Forrest said she was writing to the Health Minister about "these very real concerns" and would scrutinise budget estimate hearings.