The Independent Police Complaints Authority (IPCA) has received a complaint over police handling of the investigation into National MP Todd Barclay.
Police last week reopened their investigation into the Clutha-Southland MP and whether he secretly recorded staff in his electorate office.
The original police investigation last year was launched after an electorate staffer laid a complaint, but concluded there was not enough evidence to prosecute. Mr Barclay refused to be interviewed as part of the investigation.
The controversy ended the political career of Mr Barclay, who will no longer be standing for the seat in September's general election.
IPCA spokeswoman Sarah Goodall said the complaint was from someone not personally involved in the case.
She said it would take several weeks for the IPCA to process the complaint.