The Commerce Commission is taking a look at the nation's ports after receiving complaints that some of the maritime hubs are taking advantage of their market power.
The regulator received seven complaints about anti-competitive conduct by New Zealand ports in the June 2018 year, its Consumer Issues report shows.
Those complaints spurred the commission to start a preliminary assessment of the conduct, but it hasn't embarked on a formal investigation, a spokesperson said.
"A number of these complaints raised potential issues about various ports taking advantage of their market power in markets for the supply of services," the report said.
The regulator's annual report highlights areas of unease among the wider public and where the most harm could occur. The commission received 7,452 complaints in the period with retail telecommunications attracting the most complaints.
The commission received 144 complaints about the perceived taking advantage of power, compared to 60 in the June 2017 year.
The seven complaints related to ports were a new phenomenon and come as most of the major operators, including Auckland, Tauranga and Lyttelton have established partnerships and inland depots to secure market share to service exporters and importers.
The national port network is also under review from legislators with the upper North Island supply chain study underpinning the government's desire to integrate port, rail and road transport infrastructure.
The increased regulatory attention also comes as Hawke's Bay Regional Council considers selling down its stake in Napier Port and listing the port operator.