The Employers and Manufacturers Association says the Maritime Union should be paying costs being passed on to businesses by shipping companies affected by industrial action at Ports of Auckland.
More than 300 union members are on a three-week-long strike after months of stoppages, failed negotiations and stand-offs over proposed changes to their conditions.
Northern Employers and Manufacturers Association chief executive Kim Campbell says importers are now having to pay surcharges of up to $300 per container because of the disruption at the port.
Mr Campbell said that when ships are diverted they're often forced to travel at a higher speed to get to a more distant port.
"When you turn the throttle up on these ships the costs really go through the roof," Mr Campbell said, adding that there are also costs involved in repositioning containers during the strike.
But Auckland Council Transport Committee chairman Mike Lee says shipping lines such as Maersk, which has introduced charge of up to $300 per container, are already making more than enough money to cover the disruption costs.
Mr Lee says the port company and the union need to start treating each other like human beings again, and sort out the dispute once and for all.
Both sides are back in mediation on Thursday, with neither party confident there'll be a resoloution, after more than six months of discussions over new collective agreements.