But can’t say how often they secured a conviction
Police in Northern Ireland spent more than £700,000 on body-worn cameras - but can't state how many times their footage has been used in court.
Campaigners said it was impossible to assess claims of the equipment's value without figures covering the role it has played in criminal proceedings.
Research by Big Brother Watch found nearly three-quarters (71%) of UK police forces have spent a total of £22.7 million on 47,922 body-worn cameras.
Here, the PSNI has spent £730,000 - the third highest outlay of all UK forces. It has a total of 2,100 cameras, a Freedom of Information request by the privacy campaign group found.
However, the PSNI was unable to provide details of how many successful prosecutions had been made based on evidence obtained through cameras, citing time and cost reasons.
Renate Samson, from Big Brother Watch, said: "The police repeatedly reassure the public that body-worn cameras will enhance transparency, create better relations, and improve prosecution rates, but despite 71% of forces rolling out nearly 48,000 cameras, these benefits are yet to be conclusively proven.
"It says little for the approach to transparency that neither the police nor the Crown Prosecution Service could tell us how often footage from the cameras has been used in court proceedings.
"If the future of policing is to arm all officers with wearable surveillance, the value of the technology must be proven and not just assumed. It is not enough to tell the public they are essential policing tools if the benefits cannot be shown."
But PSNI Superintendent Kenneth Pennington said the cameras were a vital resource.
"Video evidence goes hand in hand with accountability and transparency, both of which are key elements in increasing public confidence in policing," he said.
"The PSNI is fully committed to these principles as we continue to work together with the community within the context of keeping people safe.
"In researching, acquiring and developing body-worn video, the PSNI has recognised the need to secure public legitimacy and confidence at all stages, and will continue to do so."
Supt Pennington said officers receive extensive training for the camera and the supporting technology to ensure that any footage is appropriately acquired.
Big Brother Watch called for data to be collated and published to show how often body-worn camera footage is used as evidence during court proceedings and in obtaining early guilty pleas.
Today's figures are a sharp rise compared with previous analysis, which found fewer than 3,000 cameras had been acquired for £2.2million in the UK in 2010.