Doctors are worried recent changes by Bupa will leave hospital patients with higher out-of-pocket costs.
Revealing its latest annual report card on private health insurance, the Australian Medical Association singled out the insurer's new gap cover arrangements.
The insurer would now only be providing maximum benefits for patients in hospitals with Bupa contracts, AMA President Michael Gannon said on Monday.
The association is worried the changes mean patients will not only need to confirm their preferred doctor has a gap arrangement with Bupa, but also if that doctor has admitting rights with a hospital Bupa has a contract with.
"Public confidence in private health insurance is already at an all-time low," Dr Gannon told reporters in Perth on Monday.
"These changes will further devalue policies, which are a major financial burden for Australian families, and will place dangerous pressure on the already stressed public hospital system."
Bupa clarified its changes on March 7, revealing customers will still be able to use the Medical Gap Scheme in public hospitals if they pre-book their treatment as a private patient at least two working days before they're admitted.
In the annual report card, Dr Gannon also reiterated his association's call for an end to so-called junk policies and said Australians should carefully consider what cover they need.
"We know there are more than 20,000 policy variations," he said.
The Turnbull government has announced reforms to insurance policies and how they are classified - into gold, silver, bronze and basic categories.
But the association says it's important the changes are more than rebadging with a new label.
It also warns that without affordability being addressed, insurance membership rates will continue to fall and the viability of the entire health system will be threatened.
From April 1, premiums will increase by an average 3.95 per cent.
Health Minister Greg Hunt has insisted it's the lowest approved rise in 17 years.