Nine Entertainment chairman Peter Costello and the board have backed the company’s chief executive Mike Sneesby but admitted Australia’s biggest media group should do more to prevent bullying and sexual harassment.

After a board meeting that lasted more than three hours, Mr Costello, Mr Sneesby and Nine’s human resources chief Vanessa Morley told staff that “the conversations we have had in recent days have made it clear that we need to accelerate the work we are doing to build a culture of respect and trust”.