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 1,300 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.
© AAP 2018