The Teaching Council has backtracked after warning the government this year that it lacked the statutory power to prosecute people who teach illegally.
It says it is now confident it can take such cases, but the rules still need to be clarified.
A ministerial briefing paper showed the council and the Education Ministry told the government in May and July that the Education Act did not give the council an explicit mandate to prosecute people who worked without a valid practising certificate.
It said the council was not prosecuting people because an appeal against prosecution would probably succeed.
"The concern is that, if there was an appeal to the decision to prosecute, (Council decisions on registration and disciplinary matters are appealed fairly often), it would be difficult for the Council to defend the decision to prosecute," the paper said.
The council's chief executive Lesely Hoskin told RNZ the council's understanding of the law had changed and she was confident the council did have the power to prosecute people who worked without a certificate.
"We have moved our understanding having been in conversation now with the Ministry of Education around what the intent of the law was," she said.
"Having had those conversations, it's quite clear to us that the law does describe what needs to happen. What we would like to see though is just for a little bit more clarification for a teacher as to what would happen and who would do that. So would that be done by the Ministry of Education, would that be done by the Teaching Council and in what situations?"
The briefing paper in July said it was illegal for teachers to teach in a school or early childhood centre for more than 10 days a year without a practising certificate or a limited authority to teach.
It said enforcing certification requirements was a key function of most professional regulatory bodies and it would be unusual for the council not to do it.
The paper said the council was worried that legislation did not give it an explicit role to prosecute teachers who breached the certification requirements and the ministry would support the council to make changes to the law at the earliest opportunity.
Hoskin told RNZ no law changes were needed.
She said teaching without a valid certificate was not common and the council did not have any plans to prosecute anybody.
The council told RNZ that data-matching flagged 466 records that required further investigation in the year to the end of June. It said at the end of that period only 37 of those cases were still under investigation by the council and the Ministry of Education.
"In the normal course of events, we would expect the majority of these to turn out to be false positives. However, follow-up will be made in the first instance with the teacher, then their principal and with the Board of Trustees if necessary," it said.
Groups representing teachers and principals were surprised that the council had thought it did not have the power to prosecute illegal teachers.
They said it was critical the council could enforce the profession's standards.