Kim Williams has resigned abruptly as CEO of News Corporation Australia, ending an 18-year career with the media conglomerate.

He’s being replaced by Julian Clarke, a former chairman of the company’s Victorian arm The Herald & Weekly Times, who retired from the HWT board in June.

A former CEO of satcaster Foxtel and founding CEO of Fox Studios Australia, Williams took the reins of Rupert Murdoch’s Australian publishing empire in December 2011.

He presided over the A$2bn (US$1.8bn) deal to acquire a 25% stake in Foxtel and 50% of Fox Sports from James Packer’s Consolidated Media and streamlined the newspaper organisation, which entailed hundreds of lay-offs.

Murdoch said: “Kim has been a steady and courageous leader at a time when our businesses have faced unprecedented pressure and economic challenges. I want to thank him for his unwavering commitment, and the blood, sweat and tears he has put into News Corp Australia.”

Williams said in an email to staff: “An action like this is always taken with a heavy heart and a mixed bag of feelings and reflections on a wide range of experiences with News Corp across almost 20 years. It is certainly not a decision made lightly, or without an awareness of the impact decisions like this inevitably have on many close colleagues, clients and diverse bodies within the media community.”

Prior to News, Williams served with pubcaster ABC, the Australian Film Commission and Southern Star Entertainment.

News Corp Australia is part of News Corp following the demerger which saw the entertainment assets hived off to 21st Century Fox.

Some analysts have speculated that Clarke, who is 69, will act as a place-holder until Lachlan Murdoch takes the top job at the Australian company. However, Rupert’s son has consistently denied suggestions that he will rejoin News Corp, where he is a non-executive director.

Also, as the owner of the DMG Radio network and as non-executive chairman of and a 9% shareholder in the struggling Ten Network, Lachlan could not simultaneously control a newspaper publishing company under the current cross-media laws.