NZ Police has launched an investigation into its use of external security consultants and how any surveillance undertaken on behalf of the organisation was used.

In June State Services Commissioner Peter Hughes announced that an inquiry into the use by state sector agencies of Auckland-based private investigation firm Thompson and Clark had been widened to include all government agencies.

Two agencies, the New Zealand Security Intelligence Service (SIS) and the Ministry for Primary Industries, opened investigations of their own after information came to light during inquiries into the use of Thompson and Clark.

Director-General of Security Rebecca Kitteridge launched a probe into the conduct of some SIS staff after correspondence raised concern about favourable bias towards Thompson and Clark.

Police were not included in the inquiry but today confirmed they would run their own investigation.

Commissioner Mike Bush says that while police were not within the scope of the inquiry for legislative reasons, it was important their actions were open to investigation.

"We recognise public concerns about the use of such consultants by state sector agencies," said Bush.

"Our vision is to have the trust and confidence of all and it is appropriate that police actions in this regard are closely considered to ensure we meet the expectations of the public and our own ethical standards.

"We are committed to ensuring that our investigation is consistent with the intent and purpose of the State Services Commission inquiry."

Police will liaise closely with the SSC inquiry team and seek guidance as appropriate to ensure that its own investigation is robust, transparent and conducted with the same rigour as the SSC process.

A senior detective will lead the police investigation, which is due to be completed by the end of October.

Police also released its terms of reference for the investigation but said no further comment will be made until the investigation was completed.

Their investigation will identify and report on "whether police has engaged with any external security consultants, including but not limited to Thompson & Clark Investigations Limited (TCIL), the circumstances of and reasons for any such engagement, and the nature and outcomes of the engagement with external security consultants by police".

Police said without limiting its scope, the investigation will specifically report on whether or not surveillance activities were undertaken by any external security consultants on behalf of police and, if so, the nature of any such surveillance, either generally or relating to specific individuals; and the extent to which police requested that surveillance, and/or received information relating to that surveillance.

The investigation will also look at:

• any actions undertaken as a result of information received, any internal or external advice to police relating to or produced as a result of engaging with external security consultants and/or any monitoring undertaken, including but not limited to advice relating to potential disclosure of the existence, nature or circumstances of any surveillance undertaken
• governance and reporting mechanisms (or lack thereof) relating to engagement with security consultants
• whether or not, and the extent to which, any matters identified by the investigation may have amounted to a breach of the New Zealand Police Code of Conduct.