Australia’s third-largest bank, the NAB, has become the latest big company to launch an investigation into staff underpayments.

NAB group executive for people and culture, Susan Ferrier, last week emailed staff to say the bank had hired law firm King & Wood Mallesons and audit firm PwC to conduct a review of problems with its payroll system after discovering underpayments totalling $1.3 million to 1500 employees.

“We take paying our colleagues their full entitlements extremely seriously and it is unacceptable and simply not good enough that we have not always delivered on that promise.

“I regret these errors and apologise,” Ms Ferrier said in the email.

The Finance Sector Union (FSU) on Monday called on members at NAB to take part in an urgent audit to determine the extent of the staff underpayment.

This follows the bank last week saying it had set up an independent investigation into payments to current and former employees.

The lender identified payment problems about 1500 staff and is finalising a payout totalling $1.3 million, including superannuation and interest, as compensation.

The issue mainly relates to Group 3 & 4 staff being rostered for a weekly 40-hour week instead of the contracted 38 hours.

FSU’s Wendy Streets said this had been a long-running issue and union members at NAB were being asked to document any concerns they had about their pay to be then passed on to investigators.

She estimates the number of underpayed people could far exceed 1500.

“The FSU previously sought a legal opinion which justified our concerns about underpayment problems at the bank and payment of contracted workers is now one of several significant issues which will be investigated by consultants PWC and KWM,” she said.

Others that have had to pay back millions of dollars to staff in recent months include Qantas, Woolworths, Wesfarmers and Super Retail, as wage scandals have particularly engulfed the hospitality and retail sectors in recent years.

In a statement to the ASX in February, Woolworths admitted it had missed the mark, with an estimated $315 million owed to employees after miscalculations on nine-year old entreprise bargaining agreements.

“The calculations of the salary payment shortfall involve a substantial volume of data, a high degree of complexity, interpretation, estimations, and are subject to further analysis of prior periods and the Fair Work Ombudsman’s ongoing investigation,” it said.

Earlier in February, the company behind Rebel Sport, Supercheap Auto, BCF, and Macpac, the Super Retail Group, admitted it owed staff millions in unpaid wages – on top of $53.2 million it has already declared.

In the same month, Wesfarmers admitted it discovered $24 million in so-called “payroll errors” and supermarket giant Coles announced it owed $20 million to managers of its supermarkets and liquor division over the past six years.

-with AAP