About 1000 government workers plan to strike next month over a pay dispute.
The Public Service Association said there had been a breakdown in contract negotiations with the Ministry of Business, Innovation and Employment (MBIE).
It said the ministry would not agree to a new collective agreement that aimed to ensure all of its members earned the same rates for similar work across the country.
The negotiations have been ongoing for about three months.
The union's assistant national secretary, Basil Prestidge, said workers would walk off the job for two hours on 5 November.
He said many of those striking were immigration workers at airports around the country, which may force the temporary closure of those departments.
"It's yet to be played out what other contingencies are in place, but I imagine immigration services at airports won't be able to operate at that time," he said.
"We've got people doing the same work but on different rates of pay - basically, there's a lack of fairness."
In June last year, more than 1000 MBIE workers went on strike after salary negotiations broke down.
Public services were maintained during the strike.
Mr Prestidge said the current dispute was based on "legacy issues since the formation of MBIE".