Prime Minister Helen Clark has condemned National's ACC policy but the business sector is supporting the party's commitment to open it up to competition from private insurers.
Party leader John Key announced the policy yesterday, saying a National-led government would improve the scheme and make workplaces safer.
He said opening the Workers Account to competition would be "investigated" and decisions would only be made after careful evaluation of the benefits offered, but a background paper issued with the policy left little doubt about National's intentions.
"The National Party is committed to the principles of competition and choice as the appropriate means of ensuring efficiency of ACC provision, and increasing incentives for improved workplace safety and better rehabilitation of accident victims," the paper said.
"Because there is no choice or competition, there is no real transparency around the operation of the scheme."
The previous National government opened ACC to competition and Labour re-nationalised it when it won the 1999 election.
Miss Clark said opening up the Workers Account, which handles compensation for employees and self-employed people, would have a devastating impact on the scheme.
"It works on the basis of being a large social insurance scheme," she said.
"You kick the guts out of it if you take workers' compensation out.
"With private insurers, over time our people will pay more and get much less."
ACC Minister Maryan Street and Council of Trade Union president Helen Kelly both warned that a "privatised" scheme would cost more and deliver less, but Business New Zealand chief executive Phil O'Reilly said the sector supported it.
"We would like to see employers reimbursed for the $800 million of business levies held unused in ACC reserves, and to see an end to the over-charging that caused it," he said.