Two senior government figures – Mr Eccles and health minister Jenny Mikakos – resigned after the inquiry heard evidence of their involvement in the hotel quarantine program.

In his letter to Ms McLeay,Mr O’Donohue said the non-disclosure of Professor Sutton’s emails was allegedly in breach of the legal profession’s regulations as outlined in the Australian Solicitors'Conduct Rules 2015.

He wrote that the conduct of the solicitors and in-house lawyers may have breached rules on misleading courts or boards of inquiry,the requirement for solicitors to act honestly,not bring the profession into disrepute and not make final submissions contrary to factual evidence.

“The alleged potential breach of professional legal conduct rules poses the question whether such practices have been prevalent in the conduct of other Victorian government departments or key witnesses within government influencing further evidence submitted,or not submitted,to the inquiry,” Mr O’Donohue wrote.

“Further,it is curious that unlike most other government departments and agencies represented at the inquiry,counsel acting for DHHS did not endorse the department’s submission.”

The department’s final submission was not signed by Claire Harris,QC,the barrister who represented it during the inquiry’s hearings in September. It was instead signed by solicitors from Minter Ellison.

The Age was unable to contact Ms Harris on Thursday.

Both Minter Ellison and the department’s lawyers have defended their conduct in relation to Professor Sutton’s emails,saying they had always acted in good faith and provided the inquiry with thousands of documents.

A letter from the DHHS legal team tabled on Tuesday revealed a departmental employee had raised the non-disclosure of the emails relating to Professor Sutton in late September.

One of the email chains showed Professor Sutton involved in communications with Commonwealth officials on March 27 during which the use of private security is discussed. Professor Sutton had previously told the inquiry he was not aware of private security until a virus outbreak at a Melbourne quarantine hotel two months later.

After the non-disclosure of the emails was raised by the departmental officer,the DHHS lawyers advised the inquiry that Professor Sutton told them he stood by his previous evidence.

“Professor Sutton further instructed us that he did not consider he needed to clarify his evidence and therefore the email did not need to be provided to the board for that reason,” the legal team wrote.

AfterThe Age published the text from the withheld emails on Saturday,Professor Sutton admitted he had read the March 27 email chain but had “not registered” the details about private security and so his evidence to the board remained truthful.

Professor Sutton,who has not appeared at the daily COVID-19 press briefing since Monday,released a statement on Wednesday saying that he had yet to receive a request to provide further evidence.

“When I do,I will respond fully to the board. I have always been completely honest and truthful with the board of inquiry and will continue to be,” he said.

Meantime,the Premier said he had no knowledge of the contents of a phone call between his office and Ms Neville which has emerged in the fresh evidence tendered to the inquiry.

Mr Andrews said on Thursday that he had become aware of the call through the work of the inquiry but declined to say which member of his staff had made it and said he did not know what was said.

"I can't speculate on what that was,"the Premier said.

"We will answer the questions that the inquiry has put forward and I don't want to trample on that process."