Complaints about private health insurance have experienced their largest year-on-year increase in a decade, according to the ombudsman.
Complaints about private health insurance increased by 30 per cent in the last financial year, the worst rise in a decade.
The Private Health Insurance Ombudsman received 5750 complaints in 2016/17, up from 4416 in 2015/16.
"This is an increase of over 1300 complaints within one year, which is the largest rise we have experienced over the past 10 years," the ombudsman's latest State of the Health Funds report said.
Complaints have risen significantly over the past decade, with the number of complaints in 2008/09 sitting at 2502.
The ombudsman doesn't pinpoint the cause of the latest increase, nominating problems with benefits, written information and verbal advice as factors.
Medibank enjoys a 26.9 per cent market share of the industry, but tops the complaints with 46.3 per cent.
It is followed by BUPA (with the same market share), which recorded 17.6 per cent of all complaints.
HBF recorded the highest retention rate - the percentage of fund members who have remained with the fund for two years or more - at 97 per cent.
GMHBA recorded the lowest at 63 per cent.
The results come as Australian Institute of Health and Welfare figures show 46 per cent of Australians had some form of private patient hospital cover as at March 2017.
Almost half of $14.9 billion paid out by funds in 2015/16 went to private hospitals ($7.4 billion), according to the institute's report released on Tuesday.
Primary health care received $2.6 billion, including $1.8 billion on dental services.
But patients forked out $29.5 billion in out-of-pocket costs, including $5.7 billion on dental services.
The Australian government spent $5.7 billion on the private health insurance rebate in 2015/16.