Daniel Andrews says he is disappointed no one in his government knows who made the decision to use private security guards in Victoria's quarantine hotels.
The premier apologised unreservedly to Victorians when he appeared before the state's hotel quarantine inquiry on Friday.
"Mistakes have been made in this program and answers are required," Mr Andrews said.
"I want to make it very clear to each and every member of the Victorian community that I am sorry for what has occurred here."
Victoria's second wave of coronavirus, which resulted in more than 18,000 new infections and 750 deaths, can be traced back to outbreaks among security guards at two quarantine hotels.
After six weeks of hearings, it is still not known who made the decision to use the guards instead of the police or the Australian Defence Force, who assisted in other states.
The premier, Health Minister Jenny Mikakos, Jobs Minister Martin Pakula and Police Minister Lisa Neville have all denied being involved in the decision.
Victoria Police Chief Commissioner Shane Patton, his predecessor Graham Ashton, Chief Health Officer Brett Sutton and multiple senior public servants have also pleaded ignorance.
"No one is claiming ownership of the decision, even though no one seems to have spoken against it at the time and no one who might have been the decision-maker seems to suggest if it had been them, it would have been a bad decision," counsel assisting the inquiry Rachel Ellyard said.
"There's just no one who says it was them. Are you aware of that?"
"I am," Mr Andrews replied.
"Do you know who it was?"
"No, I don't."
A number of witnesses including the head of the premier's department Chris Eccles have told the inquiry the call to use guards was a result of "collective decision-making".
But Mr Andrews said collective decision-making "does not remove accountability".
"It is very disappointing," he said.
Ms Ellyard said a potential explanation was that it "wasn't really a decision consciously made by anyone but rather a kind of creeping assumption that formed amongst a group".
"That would be even more concerning to me because that's not a decision at all. That's just a series of assumptions," Mr Andrews said.
In his statement to the inquiry, Mr Andrews said Ms Mikakos and the Department of Health and Humans Services were responsible for the running of the hotel quarantine program.
This contradicts with both Ms Mikakos and her department secretary Kym Peake's view that there was "shared accountability" with the Department of Jobs, Precincts and Regions, which was responsible for contracting hotels and security companies.
"At the start of the program, I regarded Minister Mikakos and Minister Pakula as responsible for informing cabinet about, and seeking cabinet's endorsement of, the initial overall service model and costings that had been determined for the program," Mr Andrews' statement reads.
"I then regarded Minister Mikakos as accountable for the program."
The contracts written up by the jobs department placed the responsibility of training guards, including in the use of personal protective equipment, on security companies.
Hotels were responsible for cleaning unless a returned traveller tested positive to COVID-19.
Ms Ellyard put to the premier that matters of infection control were "too important to be left to private contractors".
"Given what's at stake, given the seriousness and the infectivity of this virus, I think that's a fair statement," he replied.
Mr Andrews also conceded he was unaware of an email sent to Mr Eccles by his federal counterpart on April 8, offering ADF support.
Mr Eccles told the inquiry he wasn't sure if he had passed the email onto anyone.
"I cannot predict what outcome it may have had but I certainly would have wanted to know, because it would have presented us with options that we otherwise didn't have," Mr Andrews said.
The premier was the final witness before the $3 million inquiry, headed by retired judge Jennifer Coate.
It will hand down its final report on November 6.
Australian Associated Press