Chains such as Tesco and Sainsbury’s said safety remains their “highest priority” and that customers were given regular reminders to follow the rules.

However, Morrisons went one step further and said it would block any customer from shopping in stores if they refuse to wear a mask without medical exemption.

Morrisons

Morrions said they would be offering customers a face covering - and those who decline without an exemption would be blocked from entering the store. 

Chief executive David Potts 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.”

Sainsbury’s

At Sainsbury's, they said greeters would remind custoemrs to wear their coverings and shop alone where possible. 

A spokeswoman for Sainsbury’s said: “Safety remains our highest priority.

“We continue to have a range of measures in place to keep customers and colleagues safe in our stores.

“We have greeters outside our supermarkets and busy convenience stores to limit the number of customers coming into stores and continue to remind customers to wear face coverings and shop alone if they are able to.

“We also have posters and regular Tannoy announcements.”

Tesco

Tesco said it was still enforcing social distancing practices in store but was not looking yet at reintroducing measures such as one-way aisles.

“The safety of our customers and colleagues is our top priority and we already have extensive social distancing measures in our stores to ensure everyone can shop safely with us,” the store said on Twitter.

“We are asking all our customers to wear a face covering when visiting our stores and have prominent signs in place to inform customers of the rules.

“However, there may be some customers who are unable to wear a face covering for medical or safety reasons and we have asked our colleagues to respect that and to not challenge them directly.”

Why is this happening?

It comes as a shopworkers’ union has been “inundated” with complaints from its members, who say they are “deeply concerned” for their safety as members of the public flout in-store Covid measures.

Usdaw urged supermarkets and food retailers to revert to “stringent” restrictions and said that staff – who are classed as key workers – must be “valued, respected and protected”.

General secretary Paddy Lillis said: “Retail staff are working with the public every day and not only suffer increased abuse, but are deeply worried about catching Covid-19.

“Where safety measures are agreed, retailers need to make sure that they are being followed consistently, in every store.

“We are also very concerned by reports that too many customers are not following necessary safety measures like social distancing, wearing a face covering and only shopping for essential items.

“It is going to take some time to roll out the vaccine and we cannot afford to be complacent in the meantime, particularly with a new strain sweeping the nation.

“Many retail workers are at a greater risk of catching the virus and bringing it home to their families.

“Supermarket workers and delivery drivers have worked throughout the pandemic to keep the country supplied with essentials.

“These key workers must be valued, respected and protected.”