The eruption was "unexpected" but was not "unforeseeable", Parkes said.
He said his team has filed charges against 10 organisations and three individuals.
Of the 13 charged, 10 will face charges under the Health and Safety at Work Act and three directors or individuals will face charges relating to exercising due diligence to ensure the company meets its health and safety obligations. These hold maximum fines of $1.5 million and $300,000 respectively.
The court date is scheduled for December 15 at the Auckland District Court.
Parkes said he could not give any specifics about the charges because they are now before the court.
Parkes said WorkSafe's investigation did not include the rescue and recovery operation.
At the peak 28 people were working on the investigation. The focus in the investigation was on the events leading up to the eruption, he said.
He would not comment on whether it was appropriate to take visitors to the island.
Parkes said the question about whether tourists should have been allowed on the island is a question that will be argued in court.
Steve Milbank, the father of one of the two Kiwi survivors of the Whakaari/White Island disaster, said the report didn't tell them much.
He said it didn't reveal who the 13 parties were that were charged as the report noted they needed an opportunity to go before a judge to apply for name suppression.
He said it would be a long time before details of why they were charged would be known and the release of the report was only the first stage.
"We're not going to know anything for a while yet."
Whakaari White Island crater floor webcam image from 11am on June 9 this year. Photo / Supplied
Milbank's son Jake was a guide and aged just 19 at the time of the tragedy. He suffered horrific burns to 80 per cent of his body and will need treatment the rest of his life.
WorkSafe had one year from the incident to file charges.
Nineteen tourists and two tour guides from White Island Tours were among the dead after the volcanic island erupted during a sight-seeing tour.
Forty-seven people were on the island at the time.
Many more would have died if not for the heroic actions of tour guides, fellow tourists, helicopter charter pilots, and the work of specialist medical teams.
People lay flowers at the gate to Whakatane Wharf as preparations are made to attempt a rescue of the remaining people on White Island a day after the volcanic eruption. Photo / Stephen Parker
WorkSafe confirmed the day after the tragedy that it had launched its own investigation.
In a statement at the time, the department said: "WorkSafe New Zealand has opened a health and safety investigation into the harm and loss of life caused by the eruption."
Under law, WorkSafe can prosecute for breaches of health and safety regulations. Penalties and sanctions range from $50,000 to $3m and jail sentences of up to five years.
WorkSafe had general oversight of tourism operations on the volcanic island off the Bay of Plenty coastline.
Under regulations introduced in 2016, it required companies such as White Island Tours and the myriad of helicopter companies that offered tours to the island to undergo safety audits.
But it could not dictate access to the island as it was owned privately.
Whakaari White Island volcanic eruption survivor Kelsey Waghorn posted this picture to Instagram on May 25 this year. Photo / Supplied
Numerous lawyers in Australia and the US have been hired by Whakaari/White Island survivors and family and friends of some of the people who died.
Sydney-based lawyer Rita Yousef confirmed to the Weekend Herald she had two confirmed clients, and had also been approached by others affected by the tragedy – including some still receiving hospital care – who want to sue Royal Caribbean Group.
Most of the people killed or injured in the December 9, 2019, eruption were on a sight-seeing voyage around New Zealand on the company's Ovation of the Seas vessel. Royal Caribbean Group is the world's second biggest cruise operator.
Yousef, who specialises in travel law and public liability for Stacks Goudkamp, said the actions she was looking at were definitely not the only ones that would be seeking financial redress for the tragedy.
"I have heard there are other law firms who are taking on these cases as well. They are Australian and American [companies] so far," Yousef said from Sydney.
Yousef said the claims she was working on were restricted to Royal Caribbean Group.
That was because it was understood those who went on the fateful trip to White Island had bought their tickets direct from the cruise line, and not from the Whakatāne-White Island Tours.
The crux of their legal case will be on the level of warnings passengers were given by the vessel's crew before signing up for the tour.
