Legal action is being taken against 19 employers in the dairy industry for breaches of employment law, the Ministry of Business, Innovation and Employment (MBIE) said.
The ministry's labour inspectorate visited 29 dairy farms in nine regions during a three month operation to check their compliance with employment laws.
More than half were targeted due to information about likely non-compliance, the ministry said in a statement.
"The level of non-compliance identified during this operation was extremely high and it was disappointing to find that a significant number of farmers still do not have systems in place to keep accurate time and wage records that are compliant with employment legislation," the ministry's labour inspectorate central regional manager, Natalie Gardiner, said.
Nine of the more serious cases are being considered for filing with the Employment Relations Authority, she said.