A recent complaint to Victoria's workplace watchdog has accused Mr Ashton of ignoring the recommendations of a report into the alleged conduct of former superintendent Dean Stevenson in 2012.

Mr Ashton, who was then deputy commissioner, ordered a new probe which allowed the former high-ranking officer to remain in the job, according to a complaint by former officer David Bishop, who was an alleged victim of Mr Stevenson.

Mr Stevenson was later promoted to the rank of commander, but resigned last year after he was accused of bullying at least five other officers that prompted the force to undertake an occupational health and safety risk assessment of his conduct.

Several officers had complained about a toxic work environment, where they claimed staff were routinely berated and belittled.

Mr Stevenson was the subject of a separate investigation by the Salus taskforce over claims he inadvertently revealed inappropriate images stored on his mobile phone to a female colleague in September 2016.

A letter to one of the alleged victims from acting Assistant Commissioner of Professional Standards Command, Graham Kent, appears to confirm the existence of inappropriate images.

"As discussed, it is clear that the behaviour you experienced should not have happened. The treatment toward you by the commander was inappropriate and the images stored on his device were in breach of policy," Mr Kent wrote on January 26, 2017.

Mr Stevenson denied all allegations of misconduct when contacted for comment.

"Several investigations including independent and external investigations have identified the truth and exonerated me from any wrongdoing or misconduct. This includes an independent external review of the investigation conducted by (former commander David) Sprague," Mr Stevenson said

"In May 2018 I was contacted by Victoria Police and asked to return to work," he said.

However, Mr Bishop, who reported bullying allegations against Mr Stevenson in 2011, blames Mr Ashton for not responding to the initial report by Mr Sprague.

He accuses Mr Ashton of failing to provide a safe work environment under the Occupational Health and Safety Act, which obliges WorkSafe Victoria to investigate the complaint.

"[Mr] Ashton failed to act on the recommendations of Commander David Sprague and that Dean Stevenson went on to cause harm by bullying and other detrimental conduct towards other employees in the period between 2012 and his resignation in 2018," Mr Bishop wrote in a statement to WorkSafe on September 9.

A source familiar with the original investigation of Mr Stevenson said the findings were highly critical of his conduct and recommended disciplinary action.

"His behaviour was well known to other superintendents, but no one wanted to say anything. It was all about arse covering," the source said.

The handling of the case has fuelled a perception of double standards in the force, where lower-ranking officers face dismissal, demotion or admonishment for similar misbehaviour.

The handling of Mr Stevenson's case by force command has also strained relations with the powerful police union, particularly in May last year, when complainants were instructed that he would be returning to his post.

At the time, Police Association secretary Wayne Gatt said Victoria Police needed to improve its response to workplace conflict to ensure it was "consistently fair, transparent and robust".

"Sadly, our members' experiences in this regard are quite often different and current processes fail to consistently serve the interests of complainants or respondents," Mr Gatt told The Age.

A WorkSafe spokesman confirmed an investigation had been launched into the complaint by Mr Bishop.

"WorkSafe received a request under Section 131 of the Occupational Health and Safety Act and will investigate, as is standard practice," the spokesman said.

A Victoria Police spokeswoman declined to comment while the matter was under investigation.

Since leaving the force, Mr Stevenson has become CEO of the Bridge of Hope Foundation, which works with vulnerable women.

The charity is based in Melbourne and provides support to women who are in danger of homelessness and disadvantage because they have turned 18 and are no longer eligible for out-of-home-care support.

- The Age