Victoria Police has been accused of withholding "uncomfortable" information from a royal commission into the use of police informers.
But lawyer for the police, Renee Enbom, denied the suggestion on Tuesday that the force was taking an "adversarial approach" to the investigation.
The royal commission is investigating police dealings with informers, including Nicola Gobbo - also known as 'Lawyer X' - who was used for information during three periods from 1995 to 2009.
The commission was told former homicide detective sergeant Sol Solomon had provided a letter to Victoria Police on January 15 about his relationship with Ms Gobbo when he was investigating the execution-style gangland murders of police informant Terrence Hodson and his wife Christine in 2004.
He requested it be forwarded to the commission, but Victoria Police failed to do so.
The commission finally received the letter four months later on May 15, but not from police.
"When you read Mr Solomon's statement, which we'll get to in good course, it's one that some people might think that Victoria Police didn't want provided to the commission or found it at least uncomfortable for it to be provided to the commission," Commissioner Margaret McMurdo said.
Ms Enbom said the letter was controversial but it wasn't being deliberately withheld.
"Well you keep telling us that but there are counter-indications," Commissioner McMurdo replied.
She also said an audit of submissions should be undertaken.
The concerns about police secrecy followed a media challenge about months of suppression orders, restricting publication of parts of the hearings.
Media lawyer John-Paul Cashen spoke to the commission on Tuesday while seeking the ability for news outlets to challenge publication gag orders.
"In our view, these orders are creating a new regime of secrecy," he argued, adding it was in the public interest for matters of police processes to be discussed in public.
But Commissioner McMurdo said each suppression order needed to be evaluated on its own merits, because the public release of certain information could put lives at risk.
She described her job, working among numerous suppression orders and public interest immunity claims, like "a boxer fighting a match with one hand tied behind his back and the other bruised and bleeding".
"But I am still upright and focused on a positive conclusion," she said.
Also on Tuesday, former police detective Stephen Campbell gave evidence from a remote location due to poor health.
Mr Campbell had been accused of a $100,000 cannabis trafficking scheme in 1999, and admitted he was in a casual sexual relationship with Ms Gobbo for several years, including during his legal proceedings.
He was later acquitted of the charges.
The commission is scheduled to continue on Wednesday.
Australian Associated Press
