The MP who holds the deciding vote on partial sales of state-owned companies says the new legislation must make it very clear the firms involved cannot sell their assets, such as hydro dams, to the highest bidder.
The Government plans to sell up to 49% of state-owned companies Genesis, Meridian, Mighty River Power and Solid Energy and reduce the Crown's shareholding in Air New Zealand.
Opposition parties say the Companies Act requires directors to act in the best interests of the company, and the Crown could be over-ridden despite still being the majority shareholder.
ACT and United Future will support the partial sale of the energy companies, under their deals with National.
United Future leader Peter Dunne says it's his understanding that as the majority shareholder the Crown would still have the final say, even if the minority wanted to sell.
But he says if there's any doubt at all, an exemption from the Companies Act should be included in the legislation.
Prime Minister John Key says an exemption will not be necessary.
"The Government's going to retain majority of these companies once we've gone through the mixed ownership model, and those safeguards, if they're required, are already there.
"But, as I say, the SOEs today already sell assets," he said.