The federal opposition's health spokeswoman, Julia Gillard, says the government's decision to sell off Medibank Private is driven by party ideology.
It is understood Cabinet has approved the sale of the health fund in principle.
And the health minister, Tony Abbott, has indicated he believes the sale would give customers a better deal.
But Ms Gillard says Mr Abbott's subsequent remarks are closer to the truth.
"He basically said, 'That's what Liberal governments do, we privatise things'.
"Now I don't think that this should be an ideological decision - I think it should be a decision about what is best for Australians who have private health insurance."