Large health insurance companies are on notice that they are being monitored by the Australian Competition and Consumer Commission (ACCC) which earlier this week took NIB, the country's fourth largest health fund, to court for not informing customers it had removed certain eye procedures from a programme offering protection from out-of-pocket costs.

ACCC Chairman Rod Sims told The Australian Financial Review that more insurers are in its firing line. "We're concerned very much that the private health insurance industry as a whole doesn't seem to place the importance that we would on good communication with their members. It's fair to say they are behind other industries," he said.

The ACCC is alleging that NIB decided to remove certain eye procedures from being comprehensively covered by its Medigap Scheme but didn't inform members – including those who had previously undertaken treatments and would likely need to undertake them again.

Mr Sims said the ACCC undertook a major market study into the medical insurance industry a couple of years ago and found a number of issues from the use of "exceptionally confusing policies that were hard to compare" to the practice of undertaking "major changes in policies that were not communicated to policyholders".

He said: "Private health insurers must ensure their disclosure practices are in line with the Australian Consumer Law. Insurers should not expect consumers to bear the responsibility of making independent enquiries to find out about important changes made unilaterally by insurers."

NIB has responded, stating: "NIB rejects the position being taken by the ACCC and believes it has acted lawfully and ethically. NIB has worked collaboratively with the ACCC throughout its investigation and has already taken steps to redress many ACCC concerns."

This is the second time in less than a year that a major health insurer has been pinged by the competition watchdog for allegedly misleading customers who, as a result, have been hit with thousands of dollars in out-of-pocket expenses they were not expecting.

NIB's larger competitor, Medibank, was taken to court last year after the regulator alleged the insurer kept its members in the dark over new limits on benefits for in-hospital blood tests and scans.