The Productivity Commission is recommending wider ownership of ports to help improve efficiency.
The Government-appointed commission said current owners - local authorities such as the Otago Regional Council - and the communities they represented, were likely to benefit over the long-term from efficiency improvements.
One option for public owners seeking to improve governance was to opt out of the relevant public sector governance regime and into the stock exchange regime, the commission said.
"A stock market listing offers significant potential governance improvements for larger companies with partial public ownership.
"These benefits arise from an observable share price, reporting and continuous disclosure rules and external analysis of company decisions."
Other options included bringing in a cornerstone private shareholder, or some form of public-private partnership.
Council control of ports appeared to be motivated by some non-commercial objectives. They included regional economic development and waterfront amenities.
"Councils are likely to be able to achieve these objectives with lower levels of port ownership," the commission said.
The commission will have played into the hands of the Government which is planning partially selling state assets.
Partial listings of port companies would be welcomed by both the Government and the NZX.
The commission was established by former local government minister Rodney Hide and is chaired by Murray Sherwin, the former director-general of the Ministry of Agriculture and Forestry.
Labour Party transport spokesman Phil Twyford was critical of the commission's report saying it had recommended partial privatisation of ports without providing evidence to show that would boost productivity or profitability.
"It is disappointing the report should be so ideological. It pays scant regard to broader issues of port reform and lack of competition among the international shipping agencies. It simply asserts the problems lie in public ownership, governance and employment relations.
"Sadly, the commission does not seem to have considered that partial privatisation could give overseas shareholders a huge say in the way our ports are run."
It was vital New Zealand retained control of such strategic infrastructure. Its ports were already dependent on powerful international shipping companies and it could not afford to reduce its stake in the governance of enterprises like the Auckland waterfront, Mr Twyford said.
