Prime Minister John Key said yesterday entitlements would be cut so the corporation could keep levy increases to politically acceptable levels in the face of severe deficits.
Details will be revealed by ACC Minister Nick Smith tomorrow.
Labour's ACC spokesman David Parker said last night the Government was scaremongering because levy rises could be reduced by pushing back the date for full funding, when the corporation will have enough money to cover all its future costs.
It has already been announced that the date will be changed from 2014 to 2019 but Mr Parker said there should be a public debate before "irreversible changes" were made to ACC.
Engineering, Printing and Manufacturing Union national secretary Andrew Little said the figures around full funding should be independently reviewed.
The books were being "massaged" on the assumption of low investment returns and higher medical costs, he said.
Increasing costs and a ballooning deficit have led to signals that ACC levies could rise by at least 10 percent and as much as 50 percent.
ACC chairman John Judge said levies would need to rise as the scheme's claim liability -- the future cost of existing claims -- was $23.8b.
Current net assets, which ACC uses to cover future costs, were $11b, leaving a $12.8b gap.
Mr Judge said the future of the scheme was at risk.
Mr Key said the public needed to tell the Government how much they wanted to pay in increased levies, compared to an extension of the scheme.
"There will unquestionably be an increase but the sort of increase that's been floated over the weekend of 40-50 percent is ridiculous and unacceptable," Mr Key said.
"That is not an option on the table".
Mr Key said there would be levy increases, but the final decision was a political one which would be made by Cabinet in February next year.
There would also be around 20 changes to the legislation and regulations reducing entitlements.
Dr Smith has indicated he will also be targeting the most recent extensions to the scheme including physiotherapy subsidies.
Another area Dr Smith has mentioned is income subsidies to the families of those who commit suicide.
Mr Key said the previous Labour government used ACC as "an extension of the welfare state".
The scheme would still be comprehensive, but it would be affordable.
