WIRRAL supermarket workers have been given electronic listening devices in an attempt to protect staff from violence and abuse.

The system has been adopted by Sainsbury’s at 600 of its ‘Local’ convenience stores, including Heswall and Hoylake.

Civil liberty campaigners fear it is yet more surveillance invading people's privacy.

Small yellow signs have been placed around stores where the system operates.

A spokesman for Sainsbury’s said the device – which does not film – is activated around 30 times a week and is only used in stores where staff numbers are small.

The recorders are activated when workers feel they are threatened, or when a crime is taking place.

Nick Pickles, director or privacy and civil liberties campaign group Big Brother Watch, said: “People should not be subject to secret filming and audio recording unless there is an extremely serious situation.

“It frankly isn’t good enough to justify such an intrusive capability by posting a small sign up at the shop entrance.

“People should be clear such technology can be used and if it is being used, it should be done in a way that customers have an opportunity to complain if they feel it is not justified.

“Sainsbury’s must be transparent about how many times these systems have been used to record their customers and why.

“They should also make available much more information about how the systems work and when staff can use them.

"Without such transparency, it is impossible to have confidence that the systems are not being abused.”

A spokesman for Sainsbury’s told the Globe the device is similar to that used by the NHS, and is recommended the police.

“We do not record our customers’ conversations in store,” explained the spokesman.

“Some colleagues in small stores wear a personal safety device, which is only activated when they or other customers are threatened or when a crime is taking place and they need to raise the alarm.

“It operates for about ten seconds to help determine which emergency service to call.

“The same personal security system is used by the NHS and is recommended by the police.

“We take the safety of both our colleagues and customers extremely seriously.”

Big Brother Watch raised privacy fears in January when Merseyside Police announced it was to introduce 50 new number plate recognition camera sites across the county.