A new campaign calls for mental health and housing systems to work together to better support homeless Victorians.

Safe and stable housing is crucial to the mental health of homeless Victorians, a leading community organisation argues.

Mental health services that work with housing systems can help improve mental health conditions for rough sleepers, according to Launch Housing.

The organisation has launched a campaign to highlight the importance of secure housing for people experiencing a mental illness, in light of the Royal Commission into the Victorian Mental Health System.

Mental illness is exacerbated by the stress and trauma of homelessness, Launch Housing CEO Ben Warner said.

More than 500 vulnerable people are discharged from acute mental health care and back into homelessness each year.

"Vulnerable people are being left behind, often with tragic consequences," Mr Warner said.

"The mental health and homelessness systems are failing people with complex needs. It's not uncommon for people who are discharged into homelessness, to return repeatedly to hospital-based care, and sometimes the prison system."

The organisation said it hoped the commission would recommend more preventive programs to obtain private rental when someone has a mental health episode, more permanent supportive housing for those in recovery and more support for transitioning into housing after treatment.

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