Immigration New Zealand staff are being investigated for helping clients, family and extended family members get visas, and four have been fired for doing so, the department says.
Information released by INZ shows there were 53 investigations within the department into staff fraud and corruption over the past year, seven of which were substantiated.
Over the past five years, four staff had been fired for conflicts of interest, while two quit before investigations could be finished, acting general manager Peter Elms says.
Ten investigations are still ongoing.
"All employees are required to declare any actual, perceived or potential conflicts and personal interests on joining MBIE and as they arise during their employment," Mr Elms said.
"It is important to state at the outset that INZ... take all allegations of conflicts of interest extremely seriously."
Over the past half decade, 48 staff had been caught out in fraud, corruption and dishonesty investigations, he said.
The offending ranged from "comparatively minor breaches to very serious ones".
"There are a range of sanctions available to MBIE, including training, letters of expectation and formal warnings up to dismissal," Mr Elms said.