Two years on from the disastrous Whakaari/White Island eruption, a lawyer representing Australian victims says the regulatory shortcomings are "terrifying".

Horrific burns killed 22 people and more than a dozen others were critically injured after the volcano erupted as tourists walked around the crater on December 9, 2019.

WorkSafe has charged 13 parties with health and safety breaches, but the regulator is facing heavy criticism for its own shortfalls.

An independent report into WorkSafe's actions leading up to the eruption says it fell well short of good practice, regulating health and safety at the Bay of Plenty island.

The review was commissioned by the Minister for Workplace Relations and Safety through the Ministry of Business, Innovation and Employment (MBIE) and was carried out by David Laurenson QC,

Rita Yousef, who is acting for some Australian eruption victims and their families, is disturbed.

"It does appear that corners were cut as well, which is quite terrifying given what ended up happening."

She told RNZ her clients had been failed by many groups, before and after the tragedy, and WorkSafe was one of them.

"It is disappointing that, not only is the New Zealand compensation system extremely inadequate - if not pretty much non-existent for them - but on top of that, there is a regulator that has the responsibility to maintain and look after safety and they obviously haven't done it."

The report says unregistered operators took tourists onto the island for five years leading up the eruption and that WorkSafe knew, but didn't sanction them.

White Island Tours was registered, but its safety audits didn't assess volcanic risk, only walking hazards.

Dr Simon Connell researches accidents and the law - he is shocked by the findings.

"It is crystal clear that something has gone horribly wrong, if you can have an audit of an adventure activity on an active volcano, that doesn't take into account the safety issues caused by being on an active volcano," he says.

"That's not a subtle, technical, legal nuance point. That is a serious, serious issue in terms of mindset."

He says there is a conflict of interest for WorkSafe, being both the regulator, and the prosecutor:

"In the sense there's an incentive there for WorkSafe to point the finger elsewhere and to build a strong case that says the fault and responsibility lies elsewhere.

"If there had been an independent adventure tourism entity, that had had the role that WorkSafe had had, I would not at all be surprised to see them on the list of parties being prosecuted. And it does seem to me that's a bit of a gap here, if WorkSafe has had failings in the background of this event and there's nobody that's looking at them in terms of holding them to account via prosecution."

Professor John Hopkins heads New Zealand's Institute of Law, Emergencies and Disasters.

He says the Whakaari explosion, and the failures highlighted since, have brought the country's whole adventure activities safety system into question.

"It's not entirely clear as to who's responsible for the accreditation system, I think it's too easy to evade responsibility. And I think it creates the idea that adventure tourism is regulated in a robust way, but I don't think that's the case."

"The regulatory scheme creates the impression of safety and comfort in the adventure industry," he says.

"I would suggest that's always been weak, too weak, in my view."

The government is currently reviewing the legislation.

In a statement, WorkSafe chief executive Phil Parkes says the agency deeply regrets its shortcomings and he is "fully committed" to change.

"WorkSafe accepts that there were significant shortcomings in our implementation and enforcement of the Adventure Activities Regulations in relation to adventure activities on Whakaari," says Parkes.

"We deeply regret that and I am fully committed to improving our performance by addressing the review's recommendations.

"Most notably, we accept the review finding that we should have moved faster to enforce the registration of a helicopter operator who was resisting registration under the Health and Safety at Work (Adventure Activities) Regulations.

"We particularly welcome the review's recommendation to extend the existing regulatory scheme to introduce a group of independent technical experts, identified by an appropriate industry body, who would be available as an extra layer of assurance for the safety audits of adventure activity operators on Whakaari.

"WorkSafe has a vision of an Aotearoa New Zealand where everyone comes home from work healthy and safe. We will continue to work with businesses, workers and communities to achieve that vision."

Forty-two of the 47 people on the island in the 2019 eruption were overseas tourists, so most of them and their families are overseas, kept out by closed borders.

Rita Yousef says her clients have been contacted by WorkSafe prosecutors and the Coronial investigation team.

Some want nothing to do with this work, others want to tell their story in court.

"Somebody who's lost a limb or lost fingers versus someone who has had an injury that can heal - their recovery process can be quite different and obviously, limbs don't grow back and fingers don't grow back, so they're having to come to terms with using things like prosthetics. Overall, the effects of this disaster will never completely go away."

The trial of the 13 charged parties, including tourism companies, the island's owners, GNS Science and the National Emergency Management Agency (NEMA) starts in July 2023 - although NEMA has asked to have its charges dismissed.

-RNZ/Sam Olley.