SIGN UP for our newsletter ✉️ :

Get the latest stories delivered straight to you

WA premier 'didn't know' about Perth Mint gold doping

Western Australia's premier says he was kept in the dark about gold doping practices at Perth Mint but any taxpayer-funded buyback is "extremely unlikely".

The WA government-owned corporation has admitted it diluted gold it sold to China with the addition of silver to save money between 2018 and 2021.

An investigation by the ABC's Four Corners program found the Shanghai Gold Exchange had raised complaints about two gold bars that did not meet its strict specifications.

An internal report into the incident raised concerns "up to 100 tonnes of stock" worth billions of dollars could be recalled to Perth to be recast at taxpayers' expense.

Premier Mark McGowan held ministerial responsibility for Perth Mint for much of that period, handing the portfolio to Mines Minister Bill Johnston in April 2021.

But he said he only became aware of the doping practice on Monday when the program aired.

"I'm advised mints all over the world ... try to maximise value within the rules," the premier told reporters on Wednesday.

"The Perth Mint tried to maximise value within the rules. For four of the world's five gold exchanges, the content of silver was fine."

Mr McGowan said the issue was brought to Perth Mint's board in September 2021 but Mr Johnston was not informed until sometime last year.

Perth Mint chief executive Jason Waters, who only took the role last year, said all gold sold during the relevant period had exceeded the minimum 99.99 per cent industry standard.

He conceded it was "unacceptable" the mint had breached the tougher Shanghai specifications and exposed itself to reputational harm.

Perth Mint remains under investigation by financial crime regulator AUSTRAC, which has ordered the appointment of an external auditor to examine concerns about its compliance with anti-money laundering and counter-terrorism financing obligations.

The premier dismissed calls for a royal commission into the mint and played down talk of a taxpayer-funded buyback.

"The advice I have is that is extremely unlikely," he said.

"But we are working with the Shanghai Gold Exchange. We will make sure we have a continuing great relationship with them.

"Since this issue was identified in 2021, tonnes and tonnes of gold have been bought by the Shanghai Gold Exchange from the Perth Mint."

Mr McGowan also backed former Rio Tinto chief executive Sam Walsh to continue as the mint's chair, having served in the role for four years.

Mr Walsh is yet to comment on the revelations.

The premier said a strategic review would examine whether the mint should remain under government ownership.

Perth Mint is Australia's biggest gold refinery with a turnover of almost $22 billion last financial year.