More than 250 front line workers at Port Otago have issued strike notice including an overtime ban which will take effect from next Saturday.
It is set to be the first industrial action at the port in more than a decade.
The notice was issued following the failure of management and workers represented by the Rail and Maritime Transport Union (RMTU) and the Maritime Union of New Zealand (MUNZ) to agree to wage and worker safety concerns today.
Accordingly, the unions - who represent virtually all terminal staff at the port - have issued a 14-day notice of an overtime ban from Saturday September 7.
A port insider said the next step would be mediation but if the strike goes ahead, it would have "serious implications" across operations, as container ships simply couldn't be turned around in a standard eight-hour shift.