Senior Victorian cop Brett Guerin has resigned from the police force after being linked to racist social media comments.
The head of Victoria Police's ethical standards body Brett Guerin has quit after being linked to racist YouTube comments and after making inappropriate remarks about former colleagues.
The Assistant Commissioner and Professional Standards Command boss was last week stood down and referred to the state's anti-corruption commission for using the alias "Vernon Demerest" to make "crude and coarse" comments about people including former police commissioner Christine Nixon.
Mr Guerin resigned from the force on Monday night after Fairfax Media reported the racist YouTube comments made under the same name - a character from the 1970 film Airport.
The newspaper also reported Demerest made sexually graphic comments about AFL, rugby league and cricket games and separately claimed women shouldn't be allowed to sing the national anthem.
"The National Anthem must never be improvised. It must always be sung by a male. A baritone. And accompanied by a band. No argument. No opinion. Just fact," Demerest wrote.
Mr Guerin last week publicly apologised for making sexually inappropriate remarks on a website about Ms Nixon and ex-police union boss Paul Mullett.
"It's crude and coarse language and, you know, what I'm most ashamed about is my mother and my daughters have read it now," he told 3AW on Thursday.
"The language I used ... was completely inappropriate, embarrassing and I can understand people saying 'what the hell is this bloke doing?'."
He said he used the alias Demerest because: "If I had gone in under my own name, it would have been associated with police."
In a statement on Monday night, Victoria Police said Mr Guerin's resignation was linked to an ongoing Independent Broad-based Anti-corruption Commission investigation.
Victoria's top cop says the behaviour of Mr Guerin was unacceptable and out of character.
Chief Commissioner Graham Ashton said he accepted Mr Guerin's resignation on Monday night.
"This, to me, describes the behaviour that is abhorrent. It is the behaviour that is completely and utterly unacceptable at Victoria Police," Mr Ashton told reporters.
Victoria Police has no idea how many different aliases its professional standards boss was using to unleash inflammatory online comments.
Nor does the force know for how Mr Guerin was involved in the behaviour.
"It's probably too early to say how exactly far they go back," Mr Ashton said.
Mr Guerin's behaviour has been referred to state corruption watchdog IBAC.
"It's completely out of character with what we know the assistant commissioner has been doing," Mr Ashton said of Mr Guerin's work.
"He has been leading integrity reforms across the police and we have seen good results.
"For this to come out is a real shock to me."