The Maritime Union is accusing Ports of Auckland of refusing to appear at mediation talks.
New Zealand's biggest exporter Fonterra announced it will stop using the port at the end of January due to ongoing industrial action at the port. It will use ports at Tauranga and Napier instead.
Ports of Auckland and union members have been at loggerheads over contract negotiations for months.
Ports of Auckland chief executive Tony Gibson says workers have been offered a 10% wage rise, plus performance bonuses and control over rostering - the best offer they are able to make.
Maritime Union president Gary Parsloe told Radio New Zealand's Summer Report programme on Thursday that Mr Gibson has simply failed to show up to mediation.
"I put out statements all up to Christmas and New Year saying we'd withdraw all the strike notice if the port company came to mediation and bargained in good faith.
"And he's simply ignored that and hasn't been to mediation, hasn't wanted the strikes lifted - so who do we want to blame?"