An inmate at the jail where murdered prison officer David Black worked was found with secret spying equipment.
A watch with a camera and recorder was found during a search at Maghaberry high security prison last month, confirmed Justice Minister David Ford.
He said: "During a routine search of a prisoner on October 8 2012 he was found to be wearing a watch which had an inbuilt camera and recording facility. This is a prohibited article and was confiscated by staff. The prisoner has been charged with an offence under prison rules."
It is understood the prisoner involved was a foreign national being held within the main body of the Co Antrim jail. He was not among dissident republicans at Roe House engaged in a dirty protest which was linked to the murder of Mr Black by a new IRA grouping that claimed responsibility for his death.
The 52-year-old father of two from Cookstown was gunned down during an ambush as he drove to work on the M1 on November 1. It is understood the watch-camera could be bought for less than £100 over the internet and was not a highly sophisticated piece of equipment.
Information about the discovery was disclosed in response to a written question at the Assembly.
Lord Morrow, who tabled the question, has said there should be tighter controls in prisons.
He said: "We have to remember why prisoners are in jail - it is not for any good that they have done, rather for a crime they have committed.
"The murder of David Black demonstrates how vulnerable our prison officers are. We have got to give them as much support as possible. We must deal with issues that potentially put them at risk. The fact that this camera was found in a watch makes it worse because it was covert."
Lord Morrow added: "This comes on the day when we learn that a photograph was taken of a prison officer at Londonderry Magistrates' Court on the day that David Black was murdered. There needs to be a complete re-think on devices which permit recording, whether it is either audio or visual."