Hundreds of police officers and other force employees fear they may be "victimised" for speaking out about corruption, with some saying whistle-blowing is actively discouraged, a damning report by Victoria's corruption watchdog suggests.

The Perceptions of Corruption report by the Independent Broad-based Anti-Corruption Commission (IBAC) revealed 46 per cent of respondents within Victoria Police feared experiencing a backlash for reporting corrupt activity.

"While there are strong indications that Victoria Police respondents would report corruption for social and moral reasons, only 20 per cent of respondents felt they would be protected from victimisation if they reported corruption," the report warned.

Only 13 per cent felt the force "actively discourages the reporting of corruption".

IBAC surveyed 1,172 mostly sworn officers, as well as other public servants in the organisation.

One respondent spoke of the poor treatment they received after lifting the lid on concerning activity.

"I have come across corruption and reported it. I was ostracised and bullied for doing so," they wrote.

Another employee said "there is fear of retribution. Whilst Victoria Police is a large employer, it is also very small".

One in five officers 'wouldn't report corruption'

Twenty per cent of respondents did not agree with the need to report corruption, including the statement "if I personally observed corruption I would definitely report it".

The report concluded that whilst the vast majority of Victoria Police employees were in support of stamping out corruption, further work was needed to address the concerns of some employees around whistle-blower protections.

Victoria Police Assistant Commissioner Stephen Leane said the force was continuing to work through the sorts of issues raised in the report.

"We've been on a campaign of improving the culture for decades in Victoria Police, right from the time of [former chief commissioner] Christine Nixon through to Ken Lay and with Graham Ashton now," he said.

"If you shine a focus on it, it ensures that you're actually making change, so I congratulate IBAC for what they're doing and I congratulate successive chief commissioners."