Telecom service workers have called a two-day strike in Northland.
The employees from Downer EDI are among 900 workers upset over the demands from a new Telecom contractor that they become owner-operators.
Australian comany Vision Stream takes over the contract for the Telecom service subsidiary Chorus from September.
On Monday afternoon 120 Northland staff called a lightning strike in Whangarei and marched through town in protest.
The Engineering, Print and Manufacturing Union, which represents the workers, says independent accountants have estimated that workers will lose up to 66% of their income if they have to set up as contractors.
But a spokesperson for Chorus, Robin Kelly, says the union's claims are based on inaccurate information.
Mr Kelly says the owner-operator model will provide the employees with a long-term future.