PwC has rejected its appointment as the auditor of Russian gold mining company Petropavlovsk, in an unusual move that may signify an increased focus on corporate governance risk at the Big Four audit firm.

In a 28 July statement Petropavlovsk said the Big Four firm had not accepted its role as auditor of the company because of “significant changes” at the company’s board at its 30 June annual general meeting, including the ousting of its previous CEO and chair.