The Education Ministry has been paying a number of teachers below minimum wage.
The Primary Teachers Union says hundreds who are in their first year of teaching are heading into Term 2 on illegal rates of pay.
The Ministry's waiting for Novopay to undertake salary assessments, and in the meantime some staff are on the lowest rate, which hasn't been adjusted to take in the new minimum wage.
The fault has been blamed on the recent minimum wage hike, but NZEI's Stephanie Mills told Heather du Plessis-Allan that this happened all of last term.
She says that the teachers affected are being paid the unqualified teachers rate.
"As of the first of April 2018, that rate was beneath the 2018 minimum wage. For the last 10 weeks or so, a lot of new teachers, new to the profession or new to New Zealand, have been paid under the legal minimum wage."
She's referred their case to the migrant exploitation unit, but says that they had alerted the Ministry earlier in the term.
"We think that is unacceptable, particularly for a Government agency, and particularly at a point where there is a shortage of teachers and we are trying to attract people into the profession."
Mills says that around 60 people have provided information to show that their pay has been affected.
"We think that the Ministry has the responsibility as a Government agency to pay at least the minimum wage or more."
The Ministry of Education says it's working with payroll to adjust the minimum wage level, and pay affected teachers what they're owed.
Mills says while they wait, teachers are out of pocket.
"They're not just not paying them on their full, they are actually paying them under the legal minimum wage. I think this is more serious than simply not paying the correct salary."