The incoming chairwoman of the competition watchdog has vowed to step away from all private appointments, including acting on behalf of Lachlan Murdoch in the trust that manages the family’s multibillion-dollar stake in media companies Fox and News Corp.

Former Labor prime minister Kevin Rudd on Wednesday criticised the nomination of competition litigator Gina Cass-Gottlieb as the next chairwoman of the Australian Competition and Consumer Commission because of her long-standing ties to Rupert and Lachlan Murdoch’s media empire.