Tesco, Asda and Waitrose are the latest supermarkets to take a tougher stance on customers who refuse to wear a face covering without a medical exemption.
The move comes amid concerns that social distancing measures are not being adhered to in stores across the UK.
On Monday, Morrisons said those who decline to wear a mask without a medical exemption would not be allowed inside its shops.
Sainsbury’s also said it would challenge customers not wearing a mask as well as those shopping in groups.
A spokesperson for the firm said guidance remained “shop alone if you can” and customers with children or carers would not be refused entry.
On Tuesday, Tesco said maskless shoppers would be barred unless they are exempt in line with Government guidance,
It also called for shoppers to be “kind, patient and respectful” towards staff.
A spokesman said: “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.”
Echoing Tesco’s calls for customers to treat staff with respect, an Asda spokesman said: “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 has also followed suit and said marshals will be stationed at entrances to offer disposable masks if needed and deny entry to anyone refusing to comply.
It has also suspended click-and-collect services based within John Lewis department stores to avoid non-essential travel, while in-home services will be carried out only if “essential” to customers’ wellbeing.
Andrew Murphy, executive director of operations at Waitrose parent company, the John Lewis Partnership, said: “By insisting on the wearing of face coverings, over and above the social distancing measures we already have in place, we aim to make our shops even safer for customers.”
Asked whether Co-op Food stores will take similar steps, chief executive Jo Whitfield said all customers “must take responsibility for wearing a face mask”.
She said: “We’ve increased our in-store messaging to remind customers and Government guidance does state that the police can take measures if members of the public don’t comply with this law.”
Shopworkers’ union Usdaw earlier said that it had been “inundated” with complaints from its members – who are classed as key workers – and called for supermarkets to revert to more stringent in-store measures.
Usdaw 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.
“Many retail workers are at a greater risk of catching the virus and bringing it home to their families.
“These key workers must be valued, respected and protected.”