The Maritime Union of New Zealand said its members – a group of about 70 workers at the port- would stop work from 7am on 31 January for 48 hours.
It warned there could be further action to follow.
The union’s Bluff branch secretary Ray Fife said 60 members at South Port voted “overwhelmingly” in favour of strike action.
He said negotiations had failed to resolve the differences between management and workers.
“The base rate for waterfront workers had historically been low and was currently at $25.30 per hour,” Fife said.
“Even with skill-based pay tiers and overtime, wages were not meeting living costs for employees, many of whom have spent years with the company.”
Boosting pay rates would allow the port to retain and recruit more staff, Fife said.
South Port’s 2023 annual report said there had been a “higher than usual” staff turnover rate of 19 percent.
Fife said the union was willing to resume negotiations at any time, but it needed a realistic offer from the company.
“We hope that they will come to the table with a better proposal that reflects the value of our work,” he said.
South Port said the union had rejected what the port believed was a fair and reasonable offer; “a 6 percent guaranteed general wage increase, plus other skillset rate adjustments [overall an 8.2 percent increase on wages], with adjustments backdated to last September”.
“Naturally, we are disappointed with the strike notice, and one which seems at odds with the positive work relationships and strong health and safety culture we have built up over recent years,” chief executive Nigel Gear said.
South Port said Maritime Union members accounted for one-third of its permanent workforce.
Gear said the strike would not affect marine operations, and shipping would continue 24/7 as usual, but other services might be restricted for the duration of it.
“We will work through this with customers and port users to minimise the disruption and impact on their businesses,” he said.
Gear said South Port remained committed to resolving the industrial dispute as quickly as possible.