Meridian Energy says the electricity market does not need the wholesale change the Labour and Green parties are pushing for.
The parties have a joint policy to introduce a state agency that would be the sole buyer of electricity if they form the next Government.
Meridian chief executive Mark Binns told a Parliamentary select committee the proposal would mean less investment in renewable energy because the upfront costs are greater.
He told Nine to Noon that if the plan proceeds, the country will have to live with the consequences for 20 or 30 years.
''There are other ways we think that you can look at retail competiveness and make a few relatively minor changes in the way the market operates. You don't have to throw the baby out with the bath water.''
Mr Binns said he would like the parties to release more details of how the policy will work in practice.