Earlier, it was revealed two government agencies were also among the organisations facing charges.
White Island Tours, a private company, confirmed it is facing charges under the Health and Safety at Work Act.
Prime Minister Jacinda Ardern said both GNS Science and the National Emergency Management Agency (Nema) today acknowledged they were among those charged over the tragedy.
GNS Science monitors volcanic activity in this country, including White Island, and scientists assign an alert level for each volcano.
Nema provides leadership in reducing risk, being ready for and responding to and recovering from emergencies.
WorkSafe revealed today that 10 organisations and three individuals were facing charges, but would not divulge who they were. The organisations each face a maximum fine of $1.5 million, and the individuals face fines up to $300,000.
White Island Tours has also confirmed it has been charged with two breaches of the Health and Safety at Work Act.
Ngāti Awa Holdings, which owns White Island Tours, chairman Paul Quinn confirmed the news to the Bay of Plenty Times.
"White Island Tours Ltd has been charged with two breaches of the Health and Safety at Work Act. No employees or directors of the company have been charged," he said.
"As the legal process is ongoing we will not be making any further comment at this time."
Quinn added that at the time of the eruption, the iwi expressed their heartfelt condolences to the families in New Zealand and abroad that lost loved ones.
"We continue to include them in our prayers. Similarly to the survivors we continue to offer our love and support."
Wednesday next week, on the first anniversary of Whakaari erupting, Quinn said they would be coming together as a community to mourn the victims and pay their respects.
Ardern on 'horrific tragedy'
The confirmation of two government agencies being charged came during Ardern's post-Cabinet press conference.
She described the eruption last December that claimed 22 lives as a "horrific tragedy".
Ardern said it was an independent decision taken by WorkSafe.
"We need this to be an independent process."
Her message to the families affected was that all New Zealanders' thoughts were with those who experienced loss or injury.
"There is no easy process from here," she said.
Sick leave to double from 5 days a year to 10
Ardern said the Government was "getting down to business" with introducing new legislation, including a law change to double annual sick leave from five days to 10 days.
The new sick leave laws would bring New Zealand into line with Australia, she said.
Covid-19 has taught the world that one person's sickness could quickly become someone else's.
There was evidence that extra sick leave is actually good for workplace productivity.
She confirmed that tomorrow she would move to declare a climate emergency in the House.
This would send a "clear signal" to the private sector, Ardern said.
Within the next few weeks, Workplace Relations and Safety Minister Michael Wood will introduce legislation increasing the yearly sick leave allowance from five days to 10.
"Covid-19 has shown how important it is to stay at home when people are sick," he said.
Increasing sick days would mean fewer people would have to take unpaid sick leave.
"We do need to move past the tough-it-out culture," he said.
The Ministry of Business, Innovation and Employment estimated the total expected cost of the new policy was 0.9 per cent of the country's total wage bill, Wood said.
Amending the current rules will mean more workers can stay at home if they're sick, and more sick leave will help support working parents.
The law change also keeps the current maximum entitlement of any unused sick leave at 20 days annually, which will help make it easier for businesses to implement.
Increasing sick leave was one of Labour's pre-election promises.
The announcement today means the bill is expected to pass in mid-2021 and will go through the full select committee process so it's able to receive submissions.
Earlier this month, the Greens pushed Labour to rush the planned sick leave legislation through Parliament before Christmas.
"The difference between five and 10 days off could be the difference between increased community transmission of Covid-19 or not," Workplace Relations
spokeswoman Jan Logie said.
But Wood said at the time although the bill would be introduced in the House before Christmas, the legislation would come into force in 2021 and would go through the normal consultation process.
National's leader Judith Collins said the policy would only make it harder for workers to keep their jobs - and would cripple businesses as they battle a recession.
"Increasing sick leave entitlements from five to 10 days a year while also increasing the minimum wage to $20 next year shows how out of touch Labour is when it comes to small business," Collins told RNZ.
In a statement today, Wood said while around half of all employers provide the current minimum entitlement of five days, many employers offer 10 days or more already.
This will mean no change for them, he said.
"But five days can be easily used up and employees who have used up their sick leave face a choice between working while sick or taking unpaid sick leave, which is not an option for many."
