ACC Minister Nick Smith announced the changes last week and published a draft bill, but he will need support from either ACT or the Maori Party to get a bare majority on a first reading.
Act had said it would look at supporting the bill and had put its policy to introduce competition into work place accident insurance on the table.
It is National Party policy to investigate opening up the part of the scheme that covers work-related personal injuries to private competition, and Act was likely to push for that.
Mr Key said it had not been possible to tie down support before the Government announced its response to ACC's proposal to increase levies.
"There are always `plan Bs', ultimately one option is that the levies increase by a larger amount," Mr Key said.
Maori Party co-leader Tariana Turia, who is also Disability Issues Minister, said she was very concerned by the idea of privatising the work account.
Costs for ACC would increase if private enterprise were able to take the only profit making part of the insurance, she said.
While some "rationing does need to happen" Mrs Turia disagreed with any reduction in the budget for house or vehicle modifications for disabled people.
She was due to talk to Dr Smith today.
