Supermarkets are getting stricter on shoppers flouting coronavirus rules after concerns that the virus is spreading in stores.

Vaccines minister Nadhim Zahawi said the government was concerned that supermarkets were becoming places where the virus could be spread more easily.

Sainsbury’s is also encouraging people to shop alone wear possible, and has hired more security guards for its stores.

A statement from Sainsbury’s chief executive Simon Roberts said: “When shopping in our stores, you must wear a mask or visor unless you have a medical exemption.  And you should also shop on your own. Thank you for your support.

“Security guards will support our colleagues at the front of store and will challenge customers who are not wearing masks or who are shopping in groups. I know you’ll understand and support what we are trying to do.

“We have also significantly reduced the number of customers allowed in our stores at any one time to ensure social distancing is maintained at all times.”

Rival Morrisons issued a similar statement. David Potts, chief executive of Morrisons, 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.”

Morrisons is also expanding its Click & Collect service to 447 stores across the UK. At the start of March 2020, there were just 14 Morrisons stores offering Click & Collect, growing to 280 in the second lockdown in November.

Click & Collect service allows customers to complete a Morrisons order online and then collect from a store, without an additional delivery charge and contact-free, at a time that suits them.

Tesco and Asda both won’t allow anyone without a mask to enter a store, unless they are exempt.

In some Tesco stores shoppers can purchase packs of face masks at the entrance, open the pack and wear one, then pay for it with their shopping later.

Tesco has also introduced a traffic light system to help limit the number of people in some stores during busy periods, and will operate a ‘one in, one out’ rule to maintain social distancing.

Aldi said it was encouraging all customers to try and reduce the number of family members they bring with them into its stores, and to shop alone if possible to support social distancing.