The decision to assess the Ruby Princess as “low risk” for coronavirus was “as inexplicable as it is unjustifiable”, a report into Australia’s biggest COVID cluster has found.

The 320-page report into the handling of the ill-fated cruise liner and its passengers was delivered to New South Wales Premier Gladys Berejiklian on Friday afternoon.

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Numerous contagious people disembarked the Ruby Princess at Circular Quay after its arrival on March 19, and subsequently spread the virus across Australia and overseas.

Among the raft of findings from the Special Commission of Inquiry commissioned by the NSW government was that authorities made serious errors by failing to test a new classification of suspected COVID-19 passengers on board.

The report noted that on March 10 the Communicable Diseases Network of Australia amended its guidelines such that everyone on board the ship with newly defined suspect cases should be tested.

But when a risk assessment was conducted on March 18, those making decisions did not have the updated definition of a “suspect case”.

“This was a serious and material error,” the commission found.

The Ruby Princess has been linked to hundreds of cases and more than 20 coronavirus-related deaths across Australia.

The ship – which was low on medical supplies and swabs for COVID-19 tests due to shortages – left Sydney on March 8 for New Zealand and returned 11 days later.

Despite the respiratory symptoms of numerous of those aboard and uncertainty surrounding test results, 2700 passengers were permitted to disembark as the voyage had been deemed low risk by NSW health authorities.

This is because only 0.94 per cent of passengers presented to the ship’s medical centre with flu-like symptoms – not the 1 per cent required to mandate NSW Health intervention – and none had visited virus-hit countries China, Italy, Iran or South Korea.

Passengers disembarked before the results of 13 expedited tests showing at least three people had the virus.

Bret Walker SC was tasked with examining the ship’s departure, arrival and disembarkation and conducted 21 days’ of hearings from April to July.

Separate NSW Police and coronial inquiries into the Ruby Princess are ongoing and not expected to report back for at least another month.

Passengers on Circular Quay after leaving the Ruby Princess in March. Photo: AAP

Before the report was made public on Thursday, the political blame game was reignited over the ill-fated disembarkation of the cruise ship.

Prime Minister Scott Morrison said it was not the Australian Border Force’s responsibility to do health checks, putting the onus back on state authorities.

“If you are looking for a doctor at the ABF, you won’t find one. That’s not their job,” he said.

“Public health is a responsibility of the state jurisdictions. That is very clearly set out.”

In March, the Prime Minister said cruise ships would be put directly under the command of border force, which is a Commonwealth agency.

-with AAP