Thousands of reports of cyber crime were quarantined on a police database instead of being investigated because software designed to protect the computer system branded them a "security risk.”

The backlog stretched to around 9,000 reports of cyber crime and fraud at one point, with some of the cases dating back to October last year.

The reports had been made to Action Fraud and handed to the National Fraud Intelligence Bureau (NFIB), run by the City of London Police. They were added to a database called Know Fraud where they are processed, assessed and distributed among investigators.

The problem was revealed by police watchdog Her Majesty's Inspectorate of Constabulary and Fire and Rescue Services (HMICFRS) in an investigation into how forces respond to cyber-dependent crime, offences which cannot be carried out without using a computer or other similar device