Nine Network chief executive Hugh Marks has addressed employees, promising free counselling after former staffers made allegations against Burke's Backyard star Don Burke for sexual misconduct.

In an email to staff on Wednesday, Mr Marks said they would take steps to ensure former employees "perhaps with old grievances" are supported, with counselling and a phone line created to allow staff to report bad behaviour.

"As much as we might like to, sometimes we unfortunately cannot rewrite history," Mr Marks said in the email.

"In light of the appalling allegations this week of sexual assault, harassment and misconduct by Don Burke I wanted to write to all staff to reaffirm Nine's commitment to maintaining a culture that is inclusive, supportive and respectful."