Peter Costello's exit from Nine Entertainment days after an altercation with a journalist will see deputy chair Catherine West take on the job of steering the media company through a rocky patch.
Ms West will step into the job after the former federal treasurer quit after being accused by the reporter of assaulting him at Canberra's airport on Thursday.
Mr Costello denied the allegation later that day, saying The Australian's Liam Mendes fell after backing into an advertising placard while asking him questions.
"I thank the board for their support over the last decade and particularly during the events of the last few weeks," Mr Costello said in a statement.
"There are enormous challenges ahead but I believe Nine is the best placed Australian media company to weather them and prosper."
Ms West thanked him for his "dedication and commitment" to the company.
"As chairman, he has always put the needs of the company first and his decision to stand down and pass on the baton of leading Nine at this time is in line with that approach."
As well as the Nine board, Ms West has served on boards at Monash IVF Group and Peter Warren Automotive and was formerly a Sky executive in the United Kingdom.
Ms West was appointed deputy chair in September 2023 after joining the board in 2016, according to Nine's corporate website.
Nine has been embroiled in scandal over the last few weeks, dealing with sexual harassment allegations within the organisation.
Australian journalist and shareholder activist Stephen Mayne said installing a female chair could help shift an industry-wide culture that's "not very friendly" towards women.
"It is quite an indictment that there's never been a female chair of a major public media company, and maybe this will lead to change in the media," he told ABC radio on Monday.
Women now make up almost 40 per cent of boards in the ASX 200 but remain rarer at the top level, Australian Institute of Company Directors data shows, making up just 9.5 per cent of chairs at those companies.
"So hopefully this will lead to further change going forward," Mr Mayne said.
Mr Costello had been chairman since 2016.
In a video published by The Australian, Mendes follows Mr Costello through the airport as he asks about Nine chief executive Mike Sneesby.
"I walked past him, he walked back into an advertising placard and he fell over," Mr Costello said.
"I did not strike him ... if he's upset about that, I'm sorry, but I did not strike him."
Mr Costello appears to walk towards the reporter at one point before the journalist falls backwards.
"You have just assaulted me," Mr Mendes says in the video.
Labor Treasurer Jim Chalmers criticised Mr Costello and said if anyone knew it was really important to treat journalists with respect, "it should be the chairman of a major media organisation".
