The Ministry of Education is under fire after it was revealed that a number of teachers have been paid below the minimum wage. 

While many cases related to overseas teachers who were recruited to help fill the teacher shortage, some New Zealand teachers were also affected. 

The union, the NZ Educational Institute (NZEI), has referred three cases to the Labour Inspectorate's migrant exploitation unit and says at least 60 NZ-trained teachers are also being paid below the minimum wage.

The Ministry of Education has confirmed "there are a small number of teachers who are being paid below the minimum wage" because their qualifications and experience are still being assessed to determine their correct pay rates.

It told the union the day before Easter that the problem would be fixed and all affected teachers would receive back pay to their correct pay rates by May 8.

However, NZEI campaign director, Stephanie Mills, told Tim Dower this is an unforgivable mistake. 

"We are in the middle of a teaching crisis and we have a Ministry of Education that says it's okay to pay people under the legal minimum wage, including people we have recruited from overseas."

"I think it is quite extraordinary and the Ministry keeps minimising the problem...but the fact is that it is illegal to pay anyone under the minimum wage."

When asked whether she thought this was deliberate exploitation, Mills says she's "not sure what you would call it".

"The Ministry must know what the legal minimum wage is, surely? It's a Government agency and people have been paid under the legal minimum wage all term - since January."

"What does it say about how we value teachers if we don't even notice that we aren't paying them legally?"

She said they have had 60 people come to them who have been paid under the legal minimum wage.

Mills said teachers "absolutely should not be in this position".

"This is not just about correcting payments, this is about the ministry breaching their obligation to pay above the legal minimum wage," she said.

The ministry's head of infrastructure service Kim Shannon said "the great majority" of teachers were paid on the correct rates.

"A small number of the teaching workforce have been impacted as a result of the new minimum wage rate applying from April 1," she said.

"We are not aware of any overseas teachers recruited by our approved recruitment providers being affected.

"However, we will reach out to our recruitment providers tomorrow to be absolutely sure that all the teachers they have recruited are on the correct pay rate. If there are any overseas teachers, including those not recruited through ministry recruiters, who are concerned about their pay rate, they should get in touch with us: [email protected]."

"We are currently working with our payroll provider to ensure that all teachers are being paid correctly. We are committed to ensuring that minimum wage adjustments are captured across all the schools' payroll workforce in the future.

"We will continue to keep schools and teachers updated."