Costello quits as Nine boss after clash with journalist

Mr Costello tangled with The Australian reporter Liam Mendes at Canberra Airport on Thursday, with video footage appearing to show him knocking over the journalist after being confronted with questions about harassment allegations at Nine.

The former treasurer has denied assaulting the journalist and said Mr Mendes tripped over an advertising placard, and was not pushed over.

Nine's board was already set to meet on Friday before the incident, but its agenda was updated to include the incident involving Mr Costello.

"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."

In a video published by The Australian, Mendes follows Mr Costello through the airport as he asks about Nine chief executive Mike Sneesby.

He had been chairman since 2016.