NSW Health says it knew influenza was circulating on the Ruby Princess cruise ship before passengers were allowed to disembark in Sydney.
Brad Hazzard has defended the governments's handling of the Ruby Princess saga as pressure mounted on the NSW Health minister.
As the state's coronavirus count grew by 104 on Saturday, Mr Hazzard staunchly stood behind his staff who had allowed the cruise ship to disembark in Sydney earlier in the month.
The government is under fire after leaked emails revealed that results of on- board swab tests of passengers who were showing signs of influenza would have been available later that day.
"The NSW Health expert panel has assessed the Ruby Princess as NOT requiring on board health assessment in Sydney," NSW Health said in the email.
A total of 622 passengers on board have tested positive for COVID-19 including 342 residing in NSW, with the handling of the saga to be investigated by NSW Police commissioner Mick Fuller.
Test results which were revealed by the government on March 20 showed that four passengers had contracted the virus while on board but by that time 2647 people had left the ship.
Labor ramped up their attack on the government, calling on the health minister to resign.
But a defiant Mr Hazzard said that NSW Health had worked "their hearts out" to keep the state safe and told critics to "take a step back".
"Can I just say that the experts who made the decision were the best in the world," Mr Hazzard said.
"And the appropriate thing at this point is for the investigation to continue.
"Each of the staff of the Chief Health Officer who made the decision made it to the best of their ability. And those people are experts in their field."
NSW Health said they were aware of 11 people who had contracted COVID-19 through close contact with Ruby Princess passengers.
NSW Chief Health Officer Dr Kerry Chant said if they had known that coronavirus was on board the ship, they would have disembarked the passengers differently and moved them to self-isolation.
But she said that would have only prevented 11 cases of the virus.
"Cases that we could have averted by decanting people in a more ordered way with face masks and taking them directly to their homes, would have been in the order of 11," Dr Chant said.
"The people that have acquired their infection on the cruise ship could not have been avoided and every period of time that people were on that cruise ship, there were actually at risk of more transmission on the cruise ship in a very, vulnerable age group. "
Over one in 10 of the state's 2493 coronavirus cases are connected to the Ruby Princess as well as seven of NSW's 12 deaths related to the virus.
Labor opposition leader Jodi McKay said the government's actions amounted to a "cover up" and slammed them for allowing the ship to disembark without testing or quarantine.
"This is one of the greatest health disasters in this state's history," she said.
"The buck stops with the health minister and we are today calling for the health minister to stand aside."