All of the big four grocers have now commited to banning customers who refuse to wear face masks in their stores without medical exemptions.

Morrisons was the first supermarket to commit to enforcing these rules, a move which was welcomed by health secretary Matt Hancock in his Monday coronavirus press conference.

Sainsbury’s, Tesco and Asda have now subsequently all also committed to enforcing mask wearing in stores and will ban people from shopping in groups. 

Chief executive Simon Roberts said the grocer would employ trained security guards at the front of stores to enforce the measures. 

Morrisons 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 Roberts said: “I’ve spent a lot of time in our stores reviewing the latest situation over the last few days and, on behalf of all my colleagues, I am asking our customers to help us keep everyone safe.

“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. Everyone’s care and consideration matters now more than ever.”

A Tesco spokeswoman said: “Since the start of the pandemic, we have focused on ensuring everyone can get the food they need in a safe environment.

“To protect our customers and colleagues, we won’t let anyone into our stores who is not wearing a face covering, unless they are exempt in line with Government guidance. We are also asking our customers to shop alone, unless they’re a carer or with children. To support our colleagues, we will have additional security in stores to help manage this.

“Our colleagues are working hard in difficult circumstances to make sure everyone can get what they need, and we’d ask everyone to please be kind, patient and respectful as we all work to keep each other safe.”

An Asda spokesman said: “We have strongly encouraged customers to wear face coverings in our stores since legislation on wearing a mask in retail spaces was introduced in July. In September we introduced 1,000 Covid Safety Marshals in our stores to work alongside our Security Colleagues monitoring face coverings, offering free coverings to customers who have forgotten theirs and encouraging adherence to social distancing guidelines. 

“We are grateful to our colleagues for their hard work in incredibly difficult circumstances and we implore customers to treat them with respect and comply with the mandatory requirement to wear a face covering unless they have a medical exemption. 

“If a customer has forgotten their face covering, we will continue to offer them  one free of charge – but should a customer refuse to wear a covering without a valid medical reason and be in any way challenging to our colleagues about doing so - our security colleagues will refuse their entry.”

Waitrose too have said they will enforce face mask measures, as part of a suite of new measures aimed at combating the growing spread of the coronavirus, including stopping click and collect from John Lewis stores. 

The announcements come amid growing concerns in government that social distancing and other measures are not being properly adhered to in supermarkets. 

Vaccines minister Nadhim Zahawi yesterday said the government’s concerns stemmed from lax enforcement of the guidelines by grocers. 

“Ultimately, the most important thing to do now is to make sure that actually enforcement – and of course the compliance with the rules – when people are going into supermarkets are being adhered to,” Mr Zahawi told Sky News.

“We need to make sure people actually wear masks and follow the one-way system,” he said.

Shopworkers’ union Usdaw also sounded alarm bells when it said it had been “inundated” with complaints from members worried about their safety at work, with many customers flouting the rules.