Unite Union is taking Burger King to the Employment Relations Authority, accusing the fast food giant of exploiting young migrant workers and running an anti-union campaign.
The union says the company has carried out a "co-ordinated, unlawful and secret campaign" to undermine the union and its relationship with members, and had discriminated against members in their employment. It is seeking remedies and penalties amounting to more than $200,000.
Antares Restaurant Group, which operates Burger King stores in New Zealand, yesterday said it had not been advised of this grievance by either the union or the authority.
Mike Treen, Unite's national director, said Burger King had "desperately resisted" signing a collective agreement with the union and was the last major fast food company to do so.
"They have always actively discouraged members from joining and because of that fact, have been successful in keeping their wages below those of their competitors," Mr Treen said.
Mr Treen said many of the victims were migrant workers from the Philippines and India, many of whom were fearful of speaking up as they depended on their jobs to qualify for residency.
"Many staff are given work permits as students ... but to get an offer for permanent residence they need to be offered a manager's job," he said.
Employee of six years Lalit Sood claimed he and other staff faced pressure from management to leave the union and he was forced to "work like a slave".
"I've always been treated very badly ... and just because I get paid a fixed salary, they expect me to work long hours and all sorts of hours," said Mr Sood.