Staffordshire Police has used special counter-terrorism powers to spy on more than 300 suspected criminals in the county over the last two years.

Suspects were secretly tracked with ‘directed surveillance’ in undisclosed locations across Staffordshire 190 times in 2008 and 176 times last year. The powers are granted under a counter-terrorism law called the Regulation of Investigatory Powers Act (RIPA) and are deemed so serious that police must obtain prior written consent from police chiefs.

They allow front line officers to covertly spy on suspects and accumulate evidence.

Data released under Freedom of Information laws shows that the biggest use of RIPA in the force is to covertly monitor suspected drugs users and dealers with 135 cases in two years.

Police spied on 33 people suspected of sex crimes, 57 burglars, 48 thieves and four they believed had guns.

But police are unable to confirm the number of convictions their covert investigations have led to.

And they refused to reveal the number of times they have used RIPA to hide cameras in people’s homes or tap into private data.

In 10 cases police tracked people suspected of minor public order offences.

But Detective Superintendent Martin Evans, Head of Serious and Organised Crime, stressed that the aim of the covert operations is to reduce crime and boost public confidence in the force.

“Directed surveillance is one of the tactics available when we proactively target individuals of organised crime groups who we believe are actively committing crime.

“The surveillance can range from planned monitoring of a CCTV camera to look for and follow someone to covertly following people around. Authority will only be given by a senior officer of Superintendent rank or above once they are satisfied that the proposed activities are proportionate and necessary.”