White Island Tours, the company that had taken visitors to Whakaari/White Island on the day of the eruption, had passed a safety audit as recently as August this year.
However WorkSafe isn't taking responsibility, saying it only supervises the auditing process done by a third party.
On Breakfast this morning, White Island Tours chair Paul Quinn said the company had passed three audits in as many years, including one in August.
Its tour groups were on the island when it erupted last Monday. Two of its guides have died, with others battling life-threatening injuries in hospital.
Mr Quinn says in the latest audit, only months before the eruption, they were "given a clean bill of health".
"We just don't know what will come out of the inquiry. We don't know whether there's going to be a review of the templates [used by the auditing company]."
The templates are approved by WorkSafe, but chief operating officer Phil Parkes says ultimately the buck stops with the companies to make sure their activities are safe.
He rejected Breakfast host John Campbell's questions over a conflict of interest in the investigation.
"I do think it's appropriate and it's because our job is to look into what happened on the island," he says.
"I'm absolutely confident that WorkSafe is the right agency to look into what happened on the island."
The audits are conducted by a third party, using a template approved by WorkSafe and overseen by WorkSafe.
It's a necessary step to be on WorkSafe's adventure activities register.
"The audits aren't pointless. The audits provide an extra layer of certainty over the primary obligation which all businesses have," Mr Parkes says.
"Sadly, even with all of the regulations in place… we know that at least 70 people die every year from injuries in workplaces."
Mr Quinn says he's not sure whether White Island Tours will continue operating, wanting to wait until the WorkSafe and coroner's inquiries are completed before considering its future.
Sixteen people have been confirmed killed in the eruption, with two others missing and presumed dead.
Forty-seven people were on the island at the time.