Police, councils and other public bodies in the UK made a total of 517,208 applications to study peoples’ email, internet and phone records last year.
The applications let authorities see “who, when and where” someone contacted someone else although not the content of the communication.
The data comes from a report of Sir Anthony May, Commissioner of the Interception of Communications, a watchdog body.
The report highlights a total of 998 errors made last year in requests for or supply of communications information.
Some of those errors resulted in innocent people being put under investigation for criminal activity, including paedophilia.
At other times, some genuine suspects managed to evade probes because their records had been deleted and the cases had to be dropped.
The report found 17 cases of “serious errors” were made, a number involving child abuse or child pornography investigations. One error can result in dozens of false leads being passed to investigators.
Joanna Cavan, head of commissioner’s office, said: “Although the numbers are small, the consequences are significant and they can be devastating.”
