In a statement, West said: “The board knows that the events of recent weeks have been extremely difficult and destabilising for our employees and other stakeholders, and we are committed to ensuring, through our cultural review and other actions announced last week, that issues will be appropriately addressed.

“The board and management are united in focusing on the wellbeing of our people in all parts of our business. At Nine, we do work that has an important value to the community, and the board and management acknowledge their responsibility to ensure all parts of business, including our newsrooms, feel supported.

“We want to ensure our people can feel proud of our company and colleagues and the work they do.”

A member of the executive leadership team suggested Costello “had to go” after Thursday’s run-in with Mendes.

Costello’s departure would “go some way to repairing the trust between the leadership team and board”, they said.

On Thursday night, Costello dismissed as “rubbish” suggestions he might be forced to resign as chair of the media company, and apologised to Mendes.

In a statement on Sunday, Costello said the board had been “supportive through the events of the last month and last few days in particular” but it now needed a new chair to unite it around a fresh vision.

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Earlier this month, Sneesby received the backing of Costello and the board over the handling of the departure of former Nine news and current affairs director Darren Wick, who was accused of drunken, lecherous behaviour.

Sneesby was considered Costello’s “captain’s pick” after Hugh Marks resigned as chief executive in 2021.

“Mr Sneesby has always had my full support as CEO,” Costello said again on Sunday. “The company has set up a robust process to investigate historical complaints which has my full support. I believe it will get to the bottom of any unknown issues.”

Senior executives suggested Costello’s departure secures Sneesby’s job, but some suggested further changes could still be required in the coming six to 12 months, alongside a further refreshment of the board.

The incident at Canberra Airport was the latest in a string of controversies surrounding Nine, which has been embroiled in scandal for several weeks over its handling of the departure of Wick.

This masthead reported that women alleged Wick had brazenly groped them, in public view of their colleagues, for years. One female former staff member said Wick’s “alcohol-fuelled grope sessions” had occurred at public Christmas parties.

The crisis reached the top levels of Nine Entertainment when it was reported Wick had been given a payout of up to $1 million and that one of Nine’s on-air stars had twice complained to a board member about Wick’s behaviour.

Sneesby last month announced Nine had commissioned an independent review into its television newsroom culture, saying the “alleged serious failings of leadership in television news clearly tells me more work needs to be done to ensure we have a safe and inclusive workplace”.

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A day after his announcement, The Australian Financial Review revealed Adrian Foo, the publicity chief of Stan, owned by Nine and formerly led by Sneesby, had left the business weeks after the company launched an internal probe into allegations of bullying and physical contact that made staff uncomfortable.

Australian Shareholders Association chief executive Rachel Waterhouse said on Sunday morning that Nine had a slew of important corporate governance policies, such as a code of conduct and Respect@Work modules, but there seemed to be a failure in implementation.

“How do you make sure those policies that are leading practice are being implemented, and how does the board and management team make sure it’s happening?” Waterhouse said.

“One retail [Nine] investor said, ‘We don’t know all the facts, but the reported [sexual assault allegations] is completely unacceptable and should’ve been addressed’.”

Costello, who finished his term as the chairman of the federal government’s Future Fund last week, was criticised by Treasurer Jim Chalmers on Friday over the airport incident.

“I think it’s really important that we treat journalists with respect, that journalists are safe in their workplace. And if anyone should know that, it should be the chairman of a major media organisation,” Chalmers said.

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