Psychiatry has topped the list of extreme fee-charging medical specialties, with those seeking vital mental health care among the hardest hit.

A report from a public policy think tank has found about 1.9 million Australians are delaying or skipping critical medical care due to exorbitant fees for specialist doctors.

The Grattan Institute report also highlights access to specialist care in Australia is a "postcode lottery", with people living in well-served areas receiving about a third more services than disadvantaged communities.

Average out-of-pocket costs for extreme-fee-charging specialists in 2023 reached $671 for psychiatry services and more than $350 for endocrinology, cardiology, paediatrics, immunology and neurology services.

The fees are resulting in "too many people are missing out on specialist mental health care", according to the Royal Australian and New Zealand College of Psychiatrists.

"Access to psychiatric care is a major issue ... along with workforce shortages, high out-of-pocket costs and maldistribution of psychiatrists in rural and remote parts of the country," the spokesperson said.

About 28.7 per cent of people who needed to see a psychiatrist either delayed or did not see one due to costs in 2023/24, according to the Australian Bureau of Statistics.

In March, concerns over access deepened when it was revealed that more than 140 of 433 psychiatrist positions were vacant in NSW, following a stand-off over pay in the public health system.

Grattan's Health Program director Peter Breadon told AAP the system was broken from start to end.

The report outlines recommendations to address these growing issues, including scrapping Medicare subsidies for specialists who charge excessive fees and publicly naming those practitioners to increase accountability.

It also urges governments to fund additional specialist appointments annually in under-serviced areas, and invest $160 million to expand training in undersupplied specialties and rural regions.

The RANZCP spokesperson told AAP it supported several of the recommendations, including the need for structural changes to improve the affordability of psychiatric care in private outpatient clinics and consulting rooms.

"Medicare is meant to be the backbone of our health system, and yet mental health services are chronically underfunded," they said.

Australian Medical Association president Danielle McMullen supports most of Grattan's recommendations, but said removing Medicare funding from specialists who charged excessive fees was not practical.

She urged leaders to sort out longer-term funding for public hospitals and develop a health workforce data tracker to show where investment was needed.

Federal Health Minister Mark Butler said private health insurers and specialists needed to do more to protect patients from exorbitant bills.