Leaked documents suggest NAB knew it was ripping off customers.

Documents leaked by a whistleblower allegedly show former NAB chairman Ken Henry knew the bank was selling faulty products while it was selling them.

The claims come from a time when EY was preparing a report for the corporate regulator, APRA.

NAB chairman Ken Henry told EY auditors that he was “confident” the bank was selling products that would later require compensation, the Sydney Morning Herald reports.

Finance Minister Mathias Cormann called on the major bank to explain itself.

“It's obviously incumbent on the banking sectors and the financial sector in general to do its bit to restore confidence, to restore public confidence,” Senator Cormann said.

“I suspect that a proper explanation today by NAB will be an important part of restoring confidence.”

NAB chief risk officer Shaun Dooley has told reporters that the bank has been open about the “significant improvements” required to address its problems.

“NAB’s program of reform includes 26 actions, which are all well underway. Executive and Board customer committees are now examining issues such as complaint handling processes and proactive identification of product hot spots,” he said.

“A review of all NAB products has commenced, with consideration of product design and how products are being used by customers.

“All significant risk matters – financial and non-financial – are detailed in reporting for NAB’s most senior risk committees. These reports are also presented to the NAB Board, the NAB Board Risk Committee and made available to APRA and our external auditor.”