A sophisticated ‘bullet beater’ designed to crack down on gun crime failed to detect five confirmed shootings on the inner-city streets of Birmingham, it has emerged.

The Shotspotter system also had to be temporarily halted last year after it failed a test exercise.

Police chiefs said the system, used successfully across America, initially struggled on British streets because of the low incidence of gunfire and the unconventional weapons typically used by gangsters.

But the system’s sensors have now been recalibrated as part of an upgrade and experts from the company behind the project are providing 24-hour analysis of any alerts.

Despite early teething troubles, the system has also been credited with helping to cut gun crime by 17 per cent. A police report into the Safe and Sound project, to be presented to West Midlands Police Authority today, (Thursday) said: “The system is, on balance, more useful than not.”

The Shotspotter can alert police to the scene of street shootings within seconds pin-pointing gunfire to within 25 metres.