The Queensland government's power generator, Stanwell Corporation, is suing Wesfarmers for hundreds of millions of dollars over what it claims are unpaid royalties from a coal mine they both own in Central Queensland.

But Wesfarmers – one of Australia's largest public companies with a market capitalisation of $43 billion – has filed a counterclaim seeking a repayment of $452 million in rebates paid for coal exported from its Curragh mine, near Blackwater, in the Bowen Basin.