The Maritime Union has filed an injunction in the Employment Court to stop Ports of Auckland continuing with its redundancy plans.
About 300 wharf workers lost their jobs last week following eight months of negotiations over a new collective contract.
The union says a hearing is to take place at the end of this month to determine the legality of the port's redundancy plans.
But it says because the port is already proceeding with its plans it has asked for the case to be heard urgently.
Union president Gary Parsloe says they could be heading to court as early as this Thursday.
He says union members met again on Tuesday and again voted against re-applying for their jobs through individual contractors, as they are determined to win them back through the legal system.
Ports of Auckland says the court action was expected.