Victoria Police is often failing to properly investigate allegations of police misconduct or assault, proving the need for an independent investigative body, a Melbourne law firm has told a parliamentary inquiry.

9 per cent of complaints substantiated

9 per cent of complaints substantiated 16 per cent of complainants not contacted by investigating officer

16 per cent of complainants not contacted by investigating officer 34 per cent of witnesses not contacted by investigating officer

34 per cent of witnesses not contacted by investigating officer 17 per cent of cases did not consider relevant evidence such as CCTV 2016 IBAC audit of police complaints system

The inquiry, which began public hearings today, is investigating whether the Independent Broad-based Anti-corruption Commission (IBAC) and other bodies are well equipped to investigate allegations of police corruption and misconduct in the state.

In its submission, Robinson Gill Lawyers said IBAC would refer 90 per cent of complaints about misconduct back to Victoria Police, which created "clear risk for a conflict of interest".

It said many clients have been awarded compensation through the legal system after Victoria Police investigators dismissed their claims as "unsubstantiated".

"The current complaints system simply isn't working," its principal lawyer Jeremy King told the inquiry.

"There is an inherent conflict of interest with police investigating themselves, and this is compounded with a lack of transparency."

He said his law firm handled up to three inquiries about police misconduct each day.

"The overwhelming majority of my clients do not want to make a complaint to Victoria Police," Mr King said.

Robinson Gill Lawyers also argued that police investigations often lacked transparency, with complainants only given limited updates and a final "brief" letter stating whether the allegations were proven or not.

It said statistics from an IBAC audit in 2016 showed 16 per cent of people who made a complaint were not contacted by the officer investigating it, while 34 per cent of witnesses were not contacted.

Only those who lodged their complaint directly with Victoria Police could submit a freedom of information request about their investigation, the law firm said.

Mr King told the inquiry this meant many people who reported their claims to IBAC — because they did not trust Victoria Police — would be prevented from finding out important details of their complaint process.

The system is not broken, Police Association says

Mr King wanted the Victorian Government to establish a new independent complaint body, or a separate body with IBAC, to investigate allegations of police misconduct.

"IBAC is a corruption commission, not a complaint body," Mr King said.

But the union representing officers argued Victoria Police had a strong track record in investigating and prosecuting officers, with 20 officers dismissed following investigations in the 2014–15 financial year.

It argued officers often felt compelled to investigate misconduct to help ensure the integrity of the force.

"I'm not convinced that the system is broken," Police Association legal manager Chris Gorissen said.

"I'm also not convinced that the public has lost confidence in the current system. I'm yet to see any real, hard, fast evidence of that."

The police union also argued against any changes to powers of IBAC.

"We would call into question, with all due respect to people who work at IBAC, the skillset that's necessary to complete those investigations with real clarity and timeliness," Mr Gorissen said.

The Police Association was asked whether police officers working at small, rural stations would feel conflicted in reporting allegations of misconduct against their colleagues.

The union admitted it was a small issue but one that did not justify an overhaul of the system.