But despite its public assurances to do the same for a royal commission into the affair, Commissioner Margaret McMurdo hammered them for hindering and delaying her work.

She highlighted the force's lack of cooperation when it came to producing documents.

"Victoria Police produced thousands of documents that were undated or had meaningless or inaccurate titles - for example, handwritten documents titled 'diary entries' with no reference to the name of the police officer to whom the diary belonged," Ms McMurdo wrote.

Among the more high profile examples was the discovery of former chief commissioner Simon Overland's police diaries in a police storage facility after he had given evidence and Inspector Martin Allison's discovery of his diaries in the roof of his house 12 months after he appeared.

In another case, metadata revealed documents identified by the force in May 2019 were not handed to the inquiry until July 2019.

The commissioner also slammed the force's broad interpretation of public interest immunity (PII) when it came to protecting information it argued was not in the public interest to be disclosed.

Under one claim, police refused to hand over 11 informer files it argued were "extremely sensitive", despite Ms McMurdo's insistence they were relevant to her work.

She has recommended an independent person be appointed to review those within three months.

She said the force often also claimed information could reveal "confidential police methodology", but did not provide rationale to support their claims.

"Victoria Police also frequently claimed PII over material that was publicly available in media reports and court records," she said.

On one occasion lawyers for Victoria Police tried to suppress the fact that officers had heard an underworld murder occur over a listening device placed in the killer's car - a storyline that featured in the Underbelly television series more than a decade ago.

They also tried to block the inquiry from hearing that officers had to press record on a recording device.

Ms McMurdo recommended legislation be changed to remove the ability for a person to refuse to comply with a notice to provide information on the basis that it is subject to a PII claim.

Attorney-General Jill Hennessy says all the commission's recommendations will be adopted.

The inquiry's work was also hampered by a significant number of historic suppression orders, which Ms McMurdo noted were not easily found.

Former Judge Frank Vincent recommended years ago that a publicly accessible database of orders be made available. Work has begun on a privately accessible database, but will only contain orders from January 2020 onwards.

"If there had been a comprehensive, central and accessible register for suppression orders while the Commission was conducting its inquiry, significant time and cost would have been saved, confusion and inadvertent breaches avoided and the safety of those who genuinely needed protection better managed," she found.

Australian Associated Press