Workers at the Port of Lyttelton who are taking industrial action over their pay dispute are outraged by the chief executive's large salary increase, the Rail and Maritime Transport Union says.
The ban on overtime by maintenance staff has shut down overnight operations at the port for the fourth weekend in a row.
A union organiser, John Kerr, said they were seeking a pay increase of between 3 and 4 percent, which is in line with settlements at other ports around the country.
"We don't see that any of those are necessarily insurmountable. It is difficult though because the CEO received an 18 percent pay increase this year and that certainly inflamed our members' expectations. But we're going to try to work around that."
Mr Kerr said he hoped the dispute could be resolved at mediation on Wednesday.
A company spokesperson said workers have been moved to other shifts to meet customer demand.