Mining giant BHP has revealed it has underpaid nearly 30,000 workers by a mammoth $430 million over more than a decade.

The miner revealed the wage discrepancies – one of largest yet seen in Australia – in a statement to the ASX on Thursday.

“A preliminary review suggests that certain rostered employees across our Australian operations have had leave incorrectly deducted on public holidays since 2010,” it said.

“There are approximately 28,500 affected current and former employees with an average of six leave days in total that have been incorrectly deducted from affected employees over this 13-year period.”

The company said the error amounted to 170,000 days across the company.

BHP said OZ Minerals, which it acquired just weeks ago, was affected by a similar leave issue. The miner has also identified 400 current and former employees at Port Hedland who are entitled to additional allowances.

“It is estimated that the cost of remediating the leave issue and the contracting issue will be up to $US280 million ($431 million), incorporating on costs including associated superannuation and interest payments,” BHP’s statement said.

The company’s Australian president, Geraldine Slattery, apologised to affected staff.

“This is not good enough and falls short of the standards we expect at BHP,” she said.

“We are working to rectify and remediate these issues, with interest, as quickly as possible.”

BHP said it would contact affected current and former employees to alert them. A dedicated hotline and website will be running from Friday.

The company said it had self-reported the issue to the Fair Work Ombudsman.

It is continuing to investigate, and pledged to provide a report with its full-year results in August.

BHP is just the latest in a string of major Australian companies to report underpayment of staff in recent years.

Woolworths has admitted to more than $600 million in underpayments over recent years, including $70 million in February.

Supermarket giant Coles is faces court action from the FWO over underpayments to thousands of staff.

Super Retail Group – the owner of Supercheap Auto, Rebel Sport, Macpac and BCF – faces similar action. It is accused of underpaying workers by more than $1 million.

In May, Mosaic Brands – Australia’s largest speciality fashion retailer –  copped a $29,000 fine for underpaying its workers’ long-service leave entitlements.

Mosaic Brands, which has 1100 stores, including brands Millers, Rivers, Katies, Rockmans and Noni B, pleaded guilty to 324 offences in Sydney’s Downing Centre Local Court. It was fined on May 19.