The Maritime Union says it could have been unloading cargo during the weekend, had waterside workers not been locked out by Ports of Auckland.
The second of two 24-hour strikes over the terms of a new collective agreement is at 10.30pm on Sunday; the first began at the same time on Thursday evening. The port company locked the workers out in the intervening period.
The company says ships carrying $300 million worth of cargo, much of it Christmas retail stock, have been diverted to other ports.
A spokesperson says the purpose of the lockout was to put pressure on the union to end the industrial action, and workers could not have unloaded the six affected ships as quickly as the union claims.
But the union's national secretary, Garry Parsloe, says that has backfired.
"We could have stopped on the Friday," he says, "gone back to work on the Saturday morning and caught up on all that backload and nobody would have been affected".
"But the company decided to lock us out on the Saturday and Sunday, so their customers, the shipping companies, couldn't have their containers picked up. So you have to ask who's to blame for that."
Ports of Auckland says mediation talks will begin on Tuesday.
The disruption has forced two ships to divert to Tauranga, where 3000 containers have been offloaded. A third ship that would have gone to Auckland is expected there on Monday; another has gone to Wellington.