"As the matter is now with IBAC for its consideration it would not be appropriate to comment further." On Thursday, Mr Guerin admitted he was behind the comments made under the name "Vernon Demerest", after the fictional character played by Dean Martin in the 1970 movie Airport. "I made a mistake with this one," he told The Age.

Using the pseudonym, Mr Guerin commented on police politics. His most vulgar remark was in defence of former chief commissioner Christine Nixon, for whom he was a staff officer, on a blog.

Former Police Association boss Paul Mullett, who was the subject of some of Mr Guerin's posts, said it was a "step in the right direction" for the Assistant Commissioner to take leave. "It's got to go through due process," he said. But he also called for IBAC to consider holding a public hearing into the allegations. "It is a significant matter of public interest. Now, to maintain that, the process should be open and transparent," he said. Mr Guerin had written under Demerest after Mr Mullet, with whom he had a long-standing dispute, lost a multimillion-dollar lawsuit against Ms Nixon in which he claimed she had plotted to oust him from his role.

Paul Mullett pictured here in 2008. Credit:Fairfax "She [Ms Nixon] bent the Mulletmeister [Mullett] over and slipped a rather large schlong up his date courtesy of the Supreme Court's decision this morning," Mr Guerin wrote. Mr Guerin also admitted to making comments on the Facebook page of the Community Advocacy Alliance, a lobby group made up of retired police officers and chaired by former Chief Commissioner Kel Glare. The alliance had been agitating some in command by criticising how the force was being run. "When Kel Glare was appointed Chief Commissioner, Ronald Reagan was President of the United States, the internet was still 10 years away and mobile phones were yet to appear. Victoria Police shot and killed more people, at a rate more than all others [sic] police forces combined, than in any other time in Australian history," Mr Guerin wrote under his pseudonym of Vernon.

He also attacked Mr Glare for talking about a female colleague's breasts and waist size, rather than her work, in his biography. "It's a valuable insight into the way this guy still thinks and shows how out-of-date he and his ilk are," he wrote. Mr Guerin said he was embarrassed and ashamed of his behaviour, but believed he was entitled to engage in reasonable public comment as a private citizen using a pseudonym. "If I put a post [under his own name] in relation to something to do with the law or a way a case was disposed of, it becomes a story," he said. "You want to bring evidence to an argument. You want to bring some balance...[but] I really made a mistake with this one."

Mr Guerin, again under the name Vernon, had also posted about Opposition leader Matthew Guy under a video on the alliance page, asking him to "please name the repeat murderer who did not serve jail time under the Andrews government". Under the Victoria Police's ethical and professional standards code, commenting on political matters is forbidden. This includes talking about the administration of any government department, with members required to appear strictly neutral in all political matters. Mr Guerin had already been reported to IBAC by the alliance after he seemingly accidentally posted under his personal account, referring to the posts by Vernon Demerest. "At least you didn't dispute the facts I wrote," part of the post said under his personal page. Under the IBAC and police act, a chief commissioner must notify the watchdog of any complaint about the conduct of themselves, a deputy commissioner or an assistant commissioner.