The corporate regulator knows of two life insurers that pay staff partly according to how many claims they deny - but is not able to publicly name them.
Fronting a House of Representatives standing committee on economics on Friday, officials from the Australian Securities and Investments Commission were repeatedly asked to reveal which insurers had the highest rates of rejected claims, and those that link remuneration to rejected claims.
Chairman Greg Medcraft said he could only do so in private, and his colleagues explained why.
"They can consent to us publicly revealing their information, but they haven't done so ... the insurers we've spoken to so far have expressed significant concern about having their identity revealed publicly," ASIC's senior executive leader Michael Saadat said.
He added that he expects the practice of linking pay to claims outcome will cease.
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The watchdog released its review of the life insurance industry this week, but the use of its powers to compel insurers to release information makes some details confidential.
"As a life insurance policy holder, I'm quite keen to know which ones are disproportionately refusing claims," Labor MP Pat Conroy said.
"Your report is quite alarming and it's important work you're doing, but your decision to use your compulsory powers has hamstrung the public's access to that information from day one."
Mr Saadat said insurers would be unlikely to voluntarily submit information on business practices without an agreement to keep it commercially confidential.
ASIC deputy chairman Peter Kell said the investigation into allegations of unethical and illegal practices at CommInsure - which has been accused of using outdated medical definitions and pressuring doctors to change opinions in order to deny claims - would be mostly complete "early in the new year".
