The spate of underpayments comes as the Albanese government considers hefty $4 million fines for workplace breaches and jail time for employers found to recklessly underpay staff or who ignore systemic pay issues.

“We are sorry to all current and former employees impacted by these errors. This is not good enough and falls short of the standards we expect at BHP. We are working to rectify and remediate these issues, with interest, as quickly as possible,” the miner’s Australian president Geraldine Slattery said.

BHP last week took aim at the Albanese government’s proposed same job, same pay workplace policy, saying it would cost the organisation up to $1.3 billion a year and threaten jobs.

The miner’s roster problems on Thursday prompted Workplace Relations Minister Tony Burke to say: “Just last week BHP were trying to assure us that their employment practices were impeccable and the government didn’t need to close any loopholes to protect wages.”

“That’s clearly not true. Australia can do better to make sure workers are properly paid. That’ll be the focus of our legislation in the coming months.”

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The company said it would contact affected current and former employees regarding remediation as soon as possible and set up a dedicated hotline and website to provide information for affected staff by Friday.

BHP said its investigations showed the leave deduction problem may also impact employees at OZ Minerals, which it recently acquired in a $9.6 billion deal.

The Mining and Energy Union said BHP’s incorrect leave payments were uncovered during a Federal Court case clarifying employee rights around public holidays under the National Employment Standards.

“The March Full Court decision in a matter brought by the Mining and Energy Union against BHP’s labour hire subsidiary Operations Services found that companies could not automatically treat public holidays as work days without first asking employees to work the days, and employees having the opportunity to refuse that request,” general secretary Grahame Kelly said.

BHP said it had identified about 400 current and former employees at Port Hedland who are entitled to additional allowances because of an error with the “employment entity in their contract”.

“Based on currently available information, it is estimated that the cost of remediating the leave issue and the contracting issue will be up to $US280 million pre-tax, incorporating on costs including associated superannuation and interest payments,” BHP said.

BHP said the investigation is ongoing, and it will update investors with further details when it reports its full-year results in August.

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