The Labour Party is defending its policy of creating a single purchaser of energy against criticism from the Government.
Labour and the Greens are promoting the policy as a way of lowering power prices which have risen at twice the inflation rate over the past four years, while the Government says it would push up prices.
Economic Development Minister Steven Joyce told TVNZ's Q+A programme on Sunday that prices climbed by 72% in the nine years of the last Labour government and the party can't be trusted to keep its promise to lower them.
Labour's finance spokesperson David Parker said the party had not been able to make changes then because profits for generators were so small.
He said generators are now in a stronger position, yet the benefits are not flowing through to consumers.