The former chief medical officer of the Commonwealth Bank's insurance arm, CommInsure, has blown the whistle on an entrenched culture of dishonest and unethical practices aimed at avoiding payouts to sick and dying people.

Key revelations from whistleblower: Doctors pressured to change opinions in bid to deny payouts

Doctors pressured to change opinions in bid to deny payouts Medical files vanished from internal system

Medical files vanished from internal system Claims assessors cherry-picked evidence to deny claims

Dr Koh revealed doctors were pressured to change their opinions, outdated medical definitions were used to deny payouts, and medical files disappeared from the internal filing system.

He said there was a culture that put profit above the interests of clients, and that legitimate claims were denied.

A joint Four Corners–Fairfax investigation has uncovered allegations of unethical and unscrupulous behaviour in CommInsure, as the Commonwealth Bank tries to rebuild its reputation after a damaging scandal in its financial planning division.

Dr Koh worked for CommInsure between November 2013 to August 2015. For privacy reasons, he asked Four Corners not to use his first name.

During his time at CommInsure, Dr Koh said doctors were urged to change their medical opinion if it did not suit the "claims strategy".

"They were quite blatant about it … 'can you please change it or delete it so that we can go to someone else to provide another opinion that's more favourable'," he said.

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Audit results never shared with medical officer

Dr Koh raised concerns after he noticed opinions were going missing from the internal IT system.

Repeated attempts to have the matter investigated were ignored.

"I did a very quick search of the record database to find out if there were similar files that'd gone missing and I uncovered a few files," he said.

"That is also in the context of claims of assessors coming to the medical team asking us to either delete opinions that we have given or to change an opinion that we have actually given because it ran counter to a claim strategy."

Dr Koh said he elevated his concerns to the CommInsure board, which commissioned an audit, but he was never told details about the investigation or its outcome.

Inside CommInsure, he also raised concerns about the use of an outdated definition to deny heart attack claims and the cherry-picking of evidence to deny claims.

He was sacked in August 2015 after being accused of sending internal documents to his personal email — a breach of IT policy.

Dr Koh said he only did this because files were going missing.

Whistleblower wrote to Commonwealth Bank CEO

Shortly after leaving the bank, he wrote to Commonwealth Bank's chief executive Ian Narev, outlining his treatment at CommInsure.

"I have raised various concerns about unethical practices … under whistleblower protection, and they were dismissed," he wrote.

"It is with much disappointment that your public proclamation of doing the right and ethical thing is only that — a public proclamation."

Sorry, this video has expired CommInsure whistleblower says insurance arm tried to avoid payouts to the sick and dying

Mr Narev said he could not comment on Dr Koh's accusations, citing legal restrictions, but said he encouraged staff to speak up if they saw something wrong.

"There are very specific provisions about how these sorts of allegations are dealt with, and they need to be dealt with by the CommInsure board, which is separate from the Commonwealth Bank board," he said.

"It's essential in a big organisation that if somebody sees something they don't think is right, they have a safe place to raise it.

"With 50,000 people, if we get 99.9 per cent right that's still 50 people who aren't doing the right thing.

"An ethical organisation can't pretend to be a perfect organisation; we will make mistakes, and therefore one of the ways we need to be judged as to whether we're an ethical organisation is the way we deal with those mistakes."