Labour and the Greens are trashing a report which says the electricity market is more efficient than their proposed alternative would be.
The report was commissioned by BusinessNZ and carried out by Sapere Research Group.
It concludes the market is highly competitive and efficient, and better able to meet the country's need than the restructured version the opposition parties are proposing.
Their flagship policy would insert a state-owned agency to buy power from the hydro companies and distribute it at a price they say would be much lower than it is now.
BusinessNZ chief executive Phil O'Reilly says it's a "rigorous analysis" of a sector that's often poorly understood by consumers.
The Greens say every family in New Zealand knows something is wrong when prices keep rising even as demand falls.
"I'm not surprised that a report commissioned by the electricity companies' lobby group says power prices are justified," said the party's energy spokesman, Gareth Hughes.
"Prices have doubled in 15 years - even though most of our power is produced at very low cost."
Labour's David Shearer says the industry is desperate to cling to its pricing model and the report can't hide the truth.
"Power prices are too high... the market is failing and all the reports in the world won't change that."
Labour and the Greens say their version would save households $300 a year.