Maritime Union members employed by the Lyttelton Port Company are striking over changes to a collective agreement, which covers members working at the container terminal.
Lyttelton Harbour Photo: 123rf.com
The union said the agreement it has been negotiating with the company covered about 160-180 employees.
The company's chief executive, Peter Davie, said the focus of the negotiations was a limited number of changes aimed at improving the alignment of work rosters with operational needs.
The aim was to "continue to improve customer services at our container terminal and remain competitive with other New Zealand ports", Mr Davie said.
The union's national secretary, Joe Fleetwood, said union members had gone on strike for the past two weekends and had given notice of strike action for the next two weekends as well.
He would not go into detail about where the negotiations had broken down.
"In the end, we have issued a legal strike notice," Mr Fleetwood said.
"There's pressures bearing down on the union, there's pressure on the company... so at the end of the day, it will get to a pressure point and we will sit down... and reach [an] agreement."
Mr Davie said the port had increased its operations to support the recovery of Kaikōura and other parts of the South Island following last November's 7.8 magnitude earthquake.
"Unfortunately, the strike action will impact on our port's ability to continue supporting the recovery," he said.
The Lyttelton Port Company had gone to court to try to stop the strikers from picketing.
On Friday, a judge ruled in the union's favour, but some conditions have been laid down.
The union is allowed to hold a peaceful non-obstructive picket in a lay-by area on Gladstone Quay during the strikes, except for half an hour either side of container terminal shift changes.