Spencer Stuart did not immediately respond to a request for comment.
Several internal candidates have put their hands up for the job but the CEO of streaming service Stan, Mike Sneesby, and Nine’s chief publishing and digital officer Chris Janz are considered the strongest contenders.
Former Nine managing director and current Foxtel executive Amanda Laing, former SBS chief Michael Ebeid and FetchTV boss Scott Lorson have all been mentioned as possible external candidates for the role.
The resignation of Mr Marks and the process to find a replacement has exposed tensions on Nine’s board, which is made up of three directors from Nine’s legacy television business and three from publishing company Fairfax Media, with which it merged in 2018.
The Nine directors are chairman Peter Costello, Samantha Lewis and Catherine West; the ex-Fairfax directors are deputy chairman Nick Falloon, Patrick Allaway and Mickie Rosen.