Co-op is secretly marking commonly stolen items including alcohol and laundry detergents with invisible “forensic spray” to track them, in the latest crackdown on shoplifting as a new law on retail crime kicks in.

The supermarket aims to use the technique across the country having tested it in Manchester and London since last year.

The spray, whichhelps the Co-op identify where stolen items are being resold and report it to the police, contains a unique forensic code for a particular location where the items were sold, which also include sweets. Police can then identify which Co-op store the items originated from when investigating physical shops or online stores suspected of reselling stolen goods.

Police forces have used similar tactics to track down stolen bikes and valuables, and protect domestic abuse victims.

The technique is part of a raft of measures which the Co-op said had helped it cut crime in its stores by a fifth last year. It said physical attacks on its staff fell by almost a third year-on-year.

Paul Gerrard, policy director at the Co-op, said: “We have made it harder to steal things and now we are making it harder to sell.”

He said the group had invested about £250m in security measures including body-worn cameras for staff, more security guards, reinforced kiosks for high-value products such as spirits and tobacco and special shelving kit which prevents large amounts of goods being swept off into a bag.

It is also testing the use of AI to help identify unusual activity via CCTV cameras in stores and alert staff so they can intervene.

The Co-op has also teamed up with police in 20 areas to share evidence such as CCTV images to catch repeat offenders. In the last year, these partnerships have resulted in 500 prolific offenders receiving custodial sentences, collectively amounting to more than 100 years.

Gerrard said: “This is not about an extra avocado going into an M&S bag. That is not the reason we are seeing crime at these levels, it is about people taking out an entire meat section for resale.”

He added police were also turning up more frequently when called to an incident – 70% of the time now compared with 20% in 2023.

He welcomed new measures under the crime and policing bill which passed into law on Wednesday after receiving royal assent. The bill includes a new standalone offence of assaulting a retail worker and will also make it easier for action to be taken when items worth less than £200 are stolen by repealing a measure which downgraded the police response to so-called “low-value shop theft”.

The police are collaborating with retailers through the “Opal project” in an attempt to tackle retail crime.

Gerrard said: “We have now got businesses taking this seriously, police taking it seriously and government taking it seriously. Everyone is pointed in the right direction and we are starting to see things improve.”

“If we want a growing economy and healthy high streets then [reducing] retail crime is a good bellwether.”

He said problems remained, with about 100 Co-op staff likely to face abuse in one day and up to four being physically attacked.

Keir Starmer said this week that the “tide could be turning” on shoplifting, pointing to a 17% rise in people charged for what has become a hot political issue.

CCTV footage that could be shared immediately with the police should be used more widely, the prime minister said, adding that “the hope of technology” could make a difference.

Official figures last year revealed annual shoplifting offences in England and Wales had passed half a million for the first time.