Union workers are blaming Lyttleton Port's "toxic culture" for a lack of movement in strike negotiations.
Workers have been on strike since Tuesday with complaints around pay and safety concerns.
Union organiser John Kerr said he doesn't know why the port company is acting like it is.
"There seems to be a culture down there that is toxic," Kerr said.
"We're a mature negotiating union. We have good relationships with the vast majority of employers we work with, including large companies like KiwiRail. Lyttleton just seems to be a special case."
Workers also say they feel alienated by the company and people are getting angry they are not listening.
The union will work over the weekend with the strike resuming next Tuesday.