National Australia Bank Ltd's (NAB) chairman said on Tuesday he...

National Australia Bank Ltd's (NAB) chairman said on Tuesday he regretted the board's failure to step in after the lender took three years to agree a refund for thousands of pension fund investors charged fees for advice they never received.

Ken Henry, a former treasury secretary, told an inquiry into financial sector misconduct he wished the board had intervened as negotiations with the corporate watchdog over a settlement stretched to three years.

It was months after the regulator sent a letter saying it was tired of negotiating, in May 2018, when the bank agreed to a settlement, the inquiry heard. The bank's pension unit agreed to pay back A$87 million ($62.8 million) in compensation to 220,000 customers.

The delay made for a tense exchange at the public inquiry, which is questioning bank CEOs and chairs in its last round of hearings due to wrap on Friday. Banks charging customers fees for services never rendered has been a central theme of the year-long inquiry.

"Do you accept that the board should have stepped in earlier?" asked a lawyer for the inquiry, Rowena Orr.

"I wish we had," replied Henry, NAB's chairman since 2015. A day earlier, Henry told the inquiry it would take a decade to fix the culture that has shredded its reputation.

The inquiry's final report due in February is expected to recommend sweeping regulatory reforms and prosecutions.

The inquiry continues its final week of public hearings with Michael Wilkins, the interim chief executive of scandal-hit wealth manager AMP Ltd (AMP) expected to be called to the stand on Tuesday afternoon.

($1 = 1.3845 Australian dollars)