Australians insured with HCF face hundreds of dollars per night in out-of-pocket fees if they are admitted to NSW public hospitals as private patients in a private room after the health fund became the latest to slash benefits.

HCF, the nation's largest non-profit fund, advised members on Monday it was clawing back higher fees charged by public hospitals in NSW and the ACT, leaving members there with out-of-pocket expenses of $320 per night.

Staying in a NSW public hospital as a private patient is about to get more expensive for HCF and Medibank members. Credit:Louise Kennerley

Private Healthcare Australia says NSW and ACT public hospitals charge $752 per night for private patients in their own rooms, compared with an average $432 in other states.

After announcing the fund will only pay NSW the equivalent of what it pays other states, a spokesman for HCF said the fund "understands acutely that affordability of private insurance is a major challenge" and was "doing all we can to help address this issue for our members".