West Australian premier Mark McGowan is facing calls to establish a royal commission into the trouble-plagued Perth Mint in the wake of allegations it sold less than pure gold to the Shanghai Gold Exchange and only stopped the practice after its biggest customer complained.

The alleged actions of the mint, officially known as Gold Corporation and owned and backed by WA government, prompted an internal investigation amid concerns the 124-year-old organisation could have to recall gold worth almost $9 billion at today’s prices.