In her response to closing submissions, Ms Mikakos says it is "implausible" to suggest no one made the decision to use private security guards in the botched program.

Lawyers assisting the inquiry last week argued the decision was not made by one person or one government department.

Instead, it pointed to a "creeping assumption that became a reality" following a 4.30pm meeting at Victoria's state control centre on March 27.

"Such a submission has insufficient regard to the realities of governmental operation and decision-making," Ms Mikakos' submission published on Friday said.

"The board ought to treat with caution the premier's evidence where he sought to explain the reference to the use of private security in the hotel quarantine program."

Mr Andrews told the inquiry he could not recall why he mentioned private security at a press conference before the March 27 meeting.

"Police, private security, all of our health team will be able to monitor compliance in a much easier way, in a static location, one hotel or a series of hotels, as the case may be," he said at the time.

In her submission, Ms Mikakos argues the premier would not have mentioned private security guards if a decision had not already been made.

Ms Mikakos said the "weight of the evidence points clearly to an actual decision, not an assumed one" being made during or soon after a meeting of National Cabinet about midday on March 27.

A Victoria Police submission to the inquiry similarly argues the decision was made before the premier's press conference.

"It is open to the board to find that, by no later than this point, a decision had been made that the proposed model would involve private security and that all interested agencies understood this," the police submission says.

The submissions from Victoria Police and Ms Mikakos point to a message written by Chief Commissioner Graham Ashton at 1.32pm on March 27, describing the appointment of private security as a "deal set up" by the Department of Premier and Cabinet.

In its submission, the department denies having any role in the decision.

Ms Mikakos resigned the day after Mr Andrews told the inquiry he held her accountable for the program, which is blamed for Victoria's devastating second wave of coronavirus.

She and Department of Health and Human Services Secretary Kym Peake had described the program as a "multi-agency operation with shared accountability".

"It would be a nonsense, it is submitted, for the DHHS, and through it, Ms Mikakos, to be considered to be solely responsible and solely accountable for the ... program," Ms Mikakos' submission says.

She said the Department of Jobs, Precincts and Regions, overseen by Minister Martin Pakula, was responsible for contracting cleaners, hotels and security guards.

Ms Mikakos' lawyers also indicated they did not cross-examine Mr Andrews or other ministers during the inquiry for fear it would be "politically disadvantageous" or "improper".

Mr Andrews said he was not interested in commenting on Ms Mikakos' submission.

"The board can draw their own conclusions, as I'm sure they will. That's exactly the role they have to play," he told reporters.

"We won't hesitate to take up the findings and any recommendations."

Opposition Leader Michael O'Brien said the inquiry should be reopened and the premier and Ms Mikakos recalled, adding "only one of them is telling the truth".

The inquiry, led by retired judge Jennifer Coate, is due to hand down its final report on November 6.

Australian Associated Press