The Independent Broad-based Anti-corruption Commission wrote to Victorian parliament's Integrity and Oversight Committee to express "grave concerns" about its inquiry into integrity agencies' witness welfare management.

IBAC said the Labor-dominated committee, under former chair Harriet Shing, made a significant departure from established procedural fairness principles during the inquiry, which was sparked by the suspected suicide of former Casey mayor Amanda Stapledon.

"We are aware that a number of confidential communications that were invited and received by the committee have been leaked to the media," it said in a five-page submission dated July 15.

"Some of these leaks plainly relate to confidential submissions that contain adverse allegations and comments about IBAC's conduct in respect of ongoing investigations and specific witnesses.

"Despite IBAC's repeated requests to have the opportunity to be heard on the matters raised in those submissions, the committee has refused to allow IBAC that opportunity, either in a public or private forum."

The leaked submissions led to widespread and inaccurate media reporting about IBAC's welfare management practices to which it couldn't respond, the submission said.

The watchdog also suggests the committee's views were improperly informed by the confidential submissions without IBAC being given the chance to review or respond to the material.

Ms Shing told staff in May to cut the video feed to the inquiry when IBAC commissioner Robert Redlich was asked why Premier Daniel Andrews was examined in private as part of the watchdog's Operation Watts and Operation Sandon investigations.

The "disappointing shortcomings" in Ms Shing's response to concerns raised by IBAC and the committee's management of the inquiry had adversely affected all entities involved.

"To avoid any irreversible damage as a result of the leaked submissions, a private hearing to canvas the issues raised in those submissions should be undertaken which would not in any way prejudice any ongoing investigation," the IBAC submission said.

Sworn into the Andrews government cabinet in June, Ms Shing was officially replaced by Gary Maas as committee chair last week - the fifth Labor MP to take on the role in four years.

Mr Maas said the language used in IBAC's submission further demonstrated why the inquiry was necessary.

"The committee work is critically important, because no agency is beyond scrutiny, especially in matters that relate to the welfare of Victorians," he tweeted on Tuesday night.

Liberal deputy chair Brad Rowswell said IBAC was within its rights to express a view and accused Mr Maas of undermining the submission, which the agency was invited to make.

"This knee-jerk response is possibly unprecedented and reeks of a limp political attack on a parliamentary process," he said.

Australian Associated Press