The Green Party has listed 93 subsidiaries of four state-owned energy companies, saying there's nothing to stop them being sold off when the companies are partially privatised.

Co-leader Russel Norman says he doesn't accept assurances that the subsidiaries will be safe because the government is going to keep control of the companies through a 51 per cent shareholding.

The government is going to sell 49 per cent of the shares in Mighty River Power, Meridian, Genesis Energy and coal miner Solid Energy.

Dr Norman thinks assets will be stripped to deliver quick returns to private shareholders and says there's not going to be anything in law to stop that happening.

"There would be enormous pressure from some private investors to generate quick returns by selling these subsidiaries," he said on Monday.

"The directors of the privatised companies would be legally obliged to act in the best interests of the company and the best interests of the minority shareholders, even if the Crown retains majority ownership."