An inquiry into the Ruby Princess cruise ship has identified “serious”, “inexcusable” and “inexplicable” mistakes by NSW Health.

Failings that led to one of Australia’s largest coronavirus outbreaks have been laid bare, with the release of the final report from an inquiry into the ill-fated voyages of the cruise ship.

But the report from the special commission of inquiry makes few recommendations, saying health authorities had recognised mistakes made, and would “do things differently if they had their time again”.

“It is inappropriate and unhelpful to make recommendations to experts that in truth amount to no more than ‘do your job’,” Commissioner Bret Walker SC said in his report.

The inquiry was established in April after thousands of passengers were allowed to leave the cruise liner at the conclusion of two separate voyages in March.

On both occasions, the ship, owned by company Princess Cruises, was docked in Sydney, and some passengers were at the time displaying COVID-19 symptoms.

In the weeks that followed, 663 of passengers tested positive for COVID-19 in Australia, and around the world, and 28 people died.

At the time, it was Australia’s worst coronavirus cluster, an undesirable title it held for months until Melbourne’s hotel quarantine debacle escalated.

The commission made several key findings, labelling some of what happened as “serious mistakes”, and “inexcusable”.

“NSW Health should have ensured that cruise ships were aware of the change to the definition of a ‘suspect case’ for COVID-19 made on 10 March,” the report said.

“This would have resulted in the identification of such cases on the Ruby Princess.

“NSW Health should also have ensured that such persons were isolated in cabins. These were serious mistakes,” it said.

The report also said the risk rating system used by NSW Health, which saw the Ruby Princess classed as low risk, which meant no action was needed, was “inexplicable as it is unjustifiable” and “a serious mistake”.

“No evidence provided to this Commission, or given by witnesses in the public hearings, comes even reasonably close to satisfactorily explaining how a decision to ‘do nothing’ by means of precaution was adequate, or rational,” the report said.

The report also criticises a directive to allow passengers to travel interstate and internationally, against public health orders.

It then takes aim at the NSW Government for not providing passengers accommodation.

“Under the terms of the Public Health Order, the State Government should have arranged suitable accommodation for all passengers who were not residents of the State,” it said.

The report only makes overarching recommendations in one chapter regarding human biosecurity arrangements, asking the state and federal departments to become more familiar with each other’s roles and responsibilities.

In one section, Mr Walker explained why he made few recommendations.

“The mistakes and failures in decision-making here have, to a large extent, been recognised by the physicians of the Expert Panel, and by NSW Health more broadly,” he said.

“They would do things differently if they had their time again.

“There are no ‘systemic’ failures to address.

“Put simply, despite the best efforts of all, some serious mistakes were made,” he said.

The NSW Premier Gladys Berejiklian said she had just received the report.

“In the public interest, and for full transparency, I am releasing it immediately,” she said.

“I will read it over the weekend and respond early next week.”

Princess Cruises said in a statement that the report confirmed “none of out people … misled public authorities involved in Ruby Princess being permitted to disembark guests.”

A NSW Police investigation into the Ruby Princess is still ongoing.