The Commonwealth Bank's insurance arm ignored the findings of police and the coroner, and refused a payout for a woman who died of an accidental prescription drug overdose because it decided she had taken her own life.

Key points: Coroner, police concluded Peta Outzen's death was accidental prescription drug overdose

Coroner, police concluded Peta Outzen's death was accidental prescription drug overdose CommInsure refused her life insurance payout as it decided her death was suicide

CommInsure refused her life insurance payout as it decided her death was suicide Father John Outzen wants an explanation from CommInsure

Peta Outzen died after taking the painkiller oxycodone at her home in Nowra, on the New South Wales south coast, in July 2014.

A police investigation and post-mortem concluded the 40-year-old mother of two died of an accidental overdose.

But when Ms Outzen's father tried to claim on her accidental death insurance policy with CBA's insurance division, CommInsure, he was told she was not covered because suicide was excluded under the policy.

"It was like a kick in the guts," John Outzen said.

"A real big kick in the guts."

Mr Outzen said he told CommInsure the police and the NSW coroner had declared his daughter's death was accidental, but the insurer refused to change its decision.

"Are they so big that they can just do what they feel like?" Mr Outzen said.

"They're actually a law unto themselves. That's what it looks like."

In a statement CommInsure's managing director Helen Troup said the insurer would review the Outzen's case.

"We are very sorry for the distress this may have caused and I intend to personally contact her family to apologise and explain the situation," she said.

However, CommInsure has made clear that given the cause of Ms Outzen's death, her family might still not be entitled to an insurance payout.

"Accidental death policies provide cover for death by injury only. These types of policies are not intended to cover non-prescribed drug use."

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'We know it wasn't suicide'

Mr Outzen wants the Commonwealth Bank to explain to him why it refused to pay out his daughter's insurance.

"They'll try to do whatever they can to get out of paying anyone for anything," he said.

7.30 has obtained copies of police statements and a coroner's report, all of which concluded that Peta Outzen's death was the result of an accidental overdose.

She was living with her father after the break-up of a long-term relationship. Mr Outzen said his daughter became depressed while living with him and started taking his pain medication.

"I'd keep what I needed for a week at a time, and then I hide the rest and just hoped that she didn't find them," he said.

One night in July 2014 Peta Outzen took a dose of oxycodone and started watching a movie on her laptop in bed. The next morning her younger brother found her dead in her bedroom.

"We know that it wasn't suicide," Mr Outzen said.

"But ... it's in print. And I think on the letter [from CommInsure] it says it twice. It's not very nice to have that distinction there that somebody committed suicide."

Bank CEOs to front hearing this week

The latest revelations about CommInsure come a day before the Commonwealth Bank's CEO Ian Narev fronts a parliamentary hearing in Canberra.

Earlier this year, a joint ABC-Fairfax investigation exposed a range of unethical behaviour at CommInsure.

The reports prompted calls from consumer groups and the Federal Opposition for a royal commission to investigate a series of scandals involving Australia's big banks.

In August, Prime Minister Malcolm Turnbull announced the CEOs of the big four banks would be asked to appear before House of Representatives Economics Committee every year.