Sainsbury’s has joined Morrisons in saying it will enforce the wearing of masks in its supermarkets, as retailers call on the police to enforce regulations inside stores. Trained security guards would be posted at shop entrances, Sainsbury’s said, to challenge any customers not wearing a mask or shopping in groups, and the number of customers allowed into stores at any one time had been significantly reduced. Simon Roberts, the supermarket’s chief executive, said: “The vast majority of customers are shopping safely, but I have also seen some customers trying to shop without a mask and shopping in larger family groups. Please help us to keep all our colleagues and customers safe by always wearing a mask and by shopping alone.” The comments came after Morrisons broke ranks with rivals by saying it would strengthen its policy on masks in particular, after the government reportedly raised concerns that falling compliance with lockdown restrictions might be contributing to the rapid rise in Covid-19. It is understood that Morrisons is prepared to call in police as a last resort if customers do not comply with requests to wear a mask. Some other British supermarkets have said they will require help from the police if the government wishes to increase the enforcement of lockdown rules, because most shop workers are not trained to handle confrontations with customers. Morrisons said it would continue to offer face coverings to customers who had forgotten them and who were not exempt from wearing them for medical reasons. David Potts, Morrisons chief executive, said: “Those who are offered a face covering and decline to wear one won’t be allowed to shop at Morrisons unless they are medically exempt. Our store colleagues are working hard to feed you and your family – please be kind.” The British Retail Consortium (BRC) said on Monday that it was “essential [that] police support the work being done by retailers”. However, multiple police sources said officers would not get involved in ensuring shoppers are wearing masks. “We won’t be doing that,” one senior police leader said, adding: “Do people really want the police telling you, ‘That’s not above your nose’? There are no extra officers, everything else [crime] is still happening. Where is the greater risk – do you put two people in a supermarket not wearing masks before a woman suffering domestic violence. “You need clearer, consistent messaging, not new rules and more enforcement.” Supermarkets have had measures in place since March to try to slow the spread of the virus, including mandatory face masks for everyone other than those with medical exemptions and social distancing. Some stores are also limiting the number of customers who can enter. However, increasing enforcement of the rules in supermarkets was one of the options being considered amid rapid increases in the number of people in hospital with Covid-19, according to government sources cited by the Telegraph. More than 6,300 people died after testing positive for Covid-19, according to government data covering the seven days up to 10 January. Supermarkets, which are classed as essential retailers, stress that they are following government rules. The BRC, which represents most of the UK’s largest food retailers, including Sainsbury’s, Asda, Waitrose and Morrisons, said data from the government’s scientific advisers showed that retail was safe, and added that its members had spent hundreds of millions of pounds on safety measures such as Perspex screens and additional cleaning. Andrew Opie, the BRC’s director of food and sustainability, said: “Supermarkets continue to follow all safety guidance, and customers should be reassured that supermarkets are Covid-secure and safe to visit during lockdown and beyond. Customers should play their part too by following in-store signage and being considerate to staff and fellow shoppers. “While enforcement of face coverings is the responsibility of the police, retailers continue to do what they can to encourage their use throughout stores. Sadly, this has led to a sharp rise in incidents of violence and abuse against shop workers, which is why it is essential that police support the work being done by retailers.” Supermarket industry sources said there was little more that retailers could do to increase enforcement without police help. “If they’re going to make it law, their officers need to be in our stores making it law,” said one person at a large retailer.