The PSNI has refused to provide details of how much money has been paid to informers in Londonderry over the past two years.
The police have also refused to give details of the number of informers handled, if any, through the Strand Road and Strabane PSNI stations.
Responding to a Freedom of Information request the force weighed up the public interest benefit of releasing the information against the cost and decided not to disclose.
It said it would “neither confirm nor deny” it held information on informers in Londonderry.
In its FOI response it said: “As has been mentioned informants play a vital role in assisting the police, and this is based very much on relationships built on trust and the expectation of complete confidentiality.
“The PSNI would never disclose information which would compromise our tactics and adversely impact on the role of informants.
“It is therefore our opinion that the balance lies in favour of non-disclosure of the information.”
Back in 2011, the Sentinel reported how the PSNI had spent over £1m paying informers between 2007 and 2011.
Police disclosed the £1,294,586 expenditure on covert human intelligence sources (CHIS) in response to a Freedom of Information (FOI) request.