Tesco has installed smoke machines in some of its stores to stop people from stealing goods after night-time break-ins.

Britain’s biggest supermarket chain uses the 4ft-high security devices in some stores at high risk of burglary outside opening hours.

The Sun first reported that the machines are brought on to the shop floor of some London stores after they are closed. If motion sensors are activated, the machine fills the store with dense fog, making it hard to see and steal goods. The machines are also fitted with a CCTV camera.

The use of the units is not new or a universal policy.

A message on the front of the machine reads: “Warning: you’re being watched. Smoke screen security fog in operation.”

A photo has been shared online of one of the devices on a shop floor in central London during opening hours. The unit was not plugged in or in use and had since been removed.

It is understood there is no plan to expand the use of the devices to other Tesco stores. The supermarket declined to comment on their use.

Shoplifting and attacks on shop workers has risen in the UK, with figures released in February showing 1,300 incidents of violence and abuse a day.

In April a British Retail Consortium report found that instances of violence and abuse in shopping centres had risen by 65% from 2021-22 to 2022-23. Body armour suppliers said demand for stab vests worn by shopping centre security staff had soared over the past two years.

The government announced plans to introduce tougher punishments for serial or abusive shoplifters in England and Wales under a new standalone criminal offence of assaulting a retail worker. The measure had been due to be appended to the criminal justice bill going through parliament this summer, but it was one of several that were dropped during May’s “wash-up” – the period when pending legislation is swiftly pushed through before an election.