Communications service providers (CSPs) were required to produce internet traffic data and telephone bill data on nearly half a million customers during 2007.

CSPs made mistakes handling around 400 of the requests out of a total of some 1,200 errors revealed in the annual report from Interception of Communications Commissioner Sir Paul Kennedy.

His report said a total of under 1,200 mistakes were made, including those of the CSPs, but said there was no evidence of abuse behind the statistics, blaming human error such as the transposition of numbers on warrants authorising tapping.

Some 1,900 warrants for actual telephone tapping were issued during the year.

Kennedy praised moves by some police forces to make the requests for information automatic, with less opportunity for keyboard input errors.

He criticised some local authorities for failing to make as much use as they could of traffic data in the investigation of housing benefit fraud and trading standards offences.