A new study is recommending a shake-up of the country's ports and of their high level of public ownership.
Business lobby group Local Government Forum commissioned the study, carried out by the New Zealand Institute of Economic Research.
The report s that efficiency in the industry appears to have stalled, with local authority ownership having some negative effects, including reducing the introduction of experienced international operators.
It suggests the country's biggest port, Ports of Auckland, may have succumbed to local pressure to retain and grow its volume of trade by undercharging international shipping lines.
The report points out that inefficiency at ports has a flow-on cost to exports and all other goods and services which involve any kind of imported component.
It makes four policy options for change, including requiring local authorities to divest their shares in port companies to prevent local interests getting in the way of making improvements in the businesses.
Ports of Auckland's managing director Jens Madsen disputes the report's ings.
Mr Madsen says the company did not have any input into the report, and worries people may be misled by its speculation and rumours.