Police have paid informants almost $2 million over the past five years but have refused to disclose specific details about the programme.
Figures released under the Official Information Act reveal police paid $343,057 to informants during 2010-11, and $1.89 million since 2006-07.
In June, the Otago Daily Times complained to the ombudsman after police declined to release district specific figures.
Detective Inspector Paul Berry, of the Police National Headquarters Covert Operations Group, said in a statement yesterday police had reconsidered some aspects of the request.
However, police declined to answer how many cases involved police informants, the payment ranges, how many crimes were solved, and how many informants negotiated times off their prison sentence.
"Police are not willing to make public operational information about its informant programme as to do so could lead to the identification of persons presumed to be linked to police as an informant," he said.
"Further, disclosing information about the programme would be likely to enable criminals to know more about the operating methods of police, enabling them to circumvent the processes in place, which would in turn place our informants and our programme at risk."
However, Det Insp Berry confirmed police would release to the ODT the criteria they used for informants, which were known as a "Covert Human Intelligence Source" (CHIS).
"[A CHIS is a] person who consciously and covertly provides information to police, whether there is an expectation of a reward or not, but there is a joint understanding that their identity will be protected and/or the CHIS actively seeks out further information on direction request or tasking from police, or there represents a threat or potential threat, danger or harm to that person as a result of the relationship between the CHIS and police and/or who supplies information to the police and due to the special circumstances relating to that information or character of that person, registration is required in order to protect that person and or the information.".
University of Canterbury sociology professor Dr Greg Newbold said informants were a legitimate but last resort for police when investigations had reached a dead end.
In cases such as a family closing ranks over the abuse of a child, the use of an informant could help bring a conviction, he said.
However, he called into question police paying prison informants, as "they are very, very, very risky and a lot have been shown to have given evidence that is totally unreliable".
"I just wouldn't accept the evidence of a prisoner informant without some form of corroboration.
"Prisoner informants are notoriously unreliable.
"Some of those guys would give up their grandmothers for five bob."
Dr Newbold said money was only offered to informants when police had reached an "investigative dead-end", and any information received would be corroborated.
Paid to informants.
Year — Amount $
• 2006-07 - $271,111
• 2007-08 - $430,178
• 2008-09 - $446,845
• 2009-10 - $400,239
• 2010-11 - $343,057
Source: New Zealand Police
