Tayside Police said systems installed in local businesses to protect staff and deter shoplifters are often not properly maintained.

Crime prevention officers are urging firms and shops with CCTV cameras to check their system is working properly.

Most large towns and cities have public CCTV monitored by police and supplemented by large stores and shops with in-house systems.

Crime prevention officer Donald Campbell said the hopes of police officers were often short-lived as vital evidence was lost due to in-house CCTV systems which were no longer fit for purpose. He said: ‘‘CCTV is not something that you fit and forget. It must be properly deployed and maintained before it can do the job it is designed for.

With the incredible number of CCTV cameras now watching Britain’s streets, you have to wonder how many of these are monitored and maintained.