The CEO of NAB has admitted that around 300 staff have been fired or left the company as a result of internal investigations into wrongdoing.

Around 300 staff of National Australia Bank have been fired or have left the company as a result of internal investigations into wrongdoing, according to its chief executive.

NAB, along with a number of prominent Australian financial institutions, has suffered from a number of compliance and customer service shortcomings during a wealth sector investigation by the Royal Commission, as reported here.

CEO Andrew Thorburn told a parliamentary committee late last week that he was ashamed of the bank's behaviour and admitted that he had been wrong to oppose a commission of inquiry which has exposed scandal after scandal in the country's greed-driven banking culture.

"It's been a particularly difficult and shameful year," Thorburn said. More than 1,200 staff have been questioned about their adherence to the bank's code of conduct as part of the internal probe, he said. Seven hundred of those questioned were found wanting and over 300, or less than one per cent of total staff, were "either terminated or have left," Thorburn admitted.

"If there's anybody who's committed a fraud or absolute clear misconduct they're terminated immediately and files in many cases are handed straight to the police," he said.

A NAB spokeswoman declined to speak to Reuters to provide further detail about which department the staff worked for or what jobs they held.

Thorburn added that "very few" of the terminations were at executive level. NAB has slashed executive pay and announced the departure of its top consumer banking executive last month after the inquiry uncovered misdeeds in his department.

The public inquiry heard that NAB's wealth management arm had charged hundreds of thousands of retirees for financial advice they never received. The banks, including NAB, have now set aside hundreds of millions of dollars for refunds, legal costs and compliance charges arising from the inquiry.