Mark McGowan has been forced to apologise over being caught swearing in the WA Parliament.

During a Question Time that largely focused on the Perth Mint gold diluting scandal, McGowan was heard muttering to his deputy Roger Cook that the issue is a “storm in a f**king teacup”.

Upon realising his blunder, McGowan then told the Legislative Assembly it was a “private and confidential” comment picked up by a microphone.

“I apologise if anyone was offended by my language,” he said, adding that he wanted “to make it clear what I said was in the context of the issue being resolved in 2021, and tonnes of gold being sold to the Shanghai Gold Exchange in the period since then.”