Ports of Auckland has been fined $40,000 for hiring strike breaking contractors during industrial action earlier this year.
In February and March the port employed an overseas engineer and local contractors to carry out engineering work when Maritime Union of New Zealand (MUNZ) members were striking over the port's contracting out plans, the union said.
The port has said it is disappointed with the fine imposed by the Employment Relations Authority (ERA).
MUNZ national president Garry Parsloe says the ERA decision places port management in an untenable position.
"Instead of focussing on settling a fair collective agreement, the port embarked on an unprincipled plan to sack their entire stevedoring workforce and replace them with contracted labour.
"Ultimately the costs of POAL's actions impact on the return to the people of Auckland."
Last month the union said it had not ruled out strike action over the Christmas break, as its dispute with Ports of Auckland drags on.
The two parties have been in facilitation at the ERA over their collective employment agreement since May 8.