The Independent Police Conduct Authority says resources are stretched in some areas of the organisation.
The police watchdog appeared before the Law and Order Select Committee in Parliament on Wednesday.
The authority says it operates on static funding and that will not increase over time.
IPCA chairperson Justice Goddard says the authority is lacking in some resources - particularly in the area of one of its core functions which is monitoring detention centres.
She says after tax, the authority has only $49,000 to monitor and report on conditions of about 450 police detention sites.
Justice Goddard says this does not really cover the salary of one person.
However, she says despite pressure on resources, the authority has managed to reduce the number of open files and investigations - even though the number of complaints has sustained.