The federal government is being urged to clarify when people with a mental illness can access support under the national disability insurance scheme.

A parliamentary committee, in a report tabled on Tuesday, said there were concerns over the eligibility criteria for people with psychosocial disabilities.

Their approval rate is one of the lowest among broad disability categories, with 81.4 per cent successful to date.

That compares to 97.5 per cent for people with intellectual disability, 98.8 per cent for people with autism and 98.9 per cent for people with cerebral palsy.

Participants found the requirements were difficult to interpret when applied disabilities related to a mental health condition, the report said.

On top of that, there was no validated assessment tool for planners to assess the eligibility of people with psychosocial disabilities.

"The reported lack of skills and expertise of planners in the mental health field adds to inconsistencies of access to the scheme," the committee concluded.

It has recommended a review of the NDIS Act and rules, as well as the development and adoption of a 'fit-for-purpose' assessment tool.

The committee has also suggested the federal, state and territory governments clarify and make public how they will provide services for people with a psychosocial disability who aren't participants in the NDIS.

On top of that, it wants COAG to conduct an audit of all services, programs and associated funding available for mental health at both state and federal levels.

Those programs and funding should be overseen and reported on by the National Mental Health Commission, it added.

It is estimated 64,000 people with psychosocial disabilities related to a mental health condition will become NDIS participants by 2019-2020.