ASDA shoppers may be asked to buy a face mask if they arrive in supermarkets without one.
It comes as part of four new coronavirus safety rules that are coming into force at Asda stores this week.
Other changes include 1,000 new marshals stationed at the front of stores and in the aisles of larger branches.
The supermarket will also be coating all its basket and trolley handles with an antimicrobial surface that prevents the spread of bacteria and viruses.
Asda already has perspex screens at checkouts and social distancing reminders in stores.
But the latest changes come after the government announced it was tightening its coronavirus restrictions following a rise in cases.
Full list of places where you need to wear a face mask
BRITS are required by law to wear a mask in the following places:
Customers in pubs and restaurants will have to cover up from September 24 but can take them off to eat or drink.
People caught not wearing a mask in shops could be fined £200.
Enforcement will be carried out by police and not retail staff.
Who doesn't have to wear a face covering?
You also don't need to wear a face covering if:
The government now says it's compulsory for shop staff to wear face masks, unless they're medically exempt.
Shoppers already have to wear a covering in stores, again, unless they're exempt or under the age of 11.
Anthony Hemmerdinger, chief operating officer at Asda, said: "Safety remains a key priority for our customers and we will continue to do all we can to keep them and our colleagues safe in store.
"These additional measures will make our stores an even safer place to shop and work during the coming months."
It comes as supermarkets including Tesco and Asda have told shoppers not to start panic-buying.
Here are some of the changes you'll find in Asda stores:
Customers may have to buy a mask
Asda shoppers may be asked to purchase a pack of disposable masks if they arrive in stores without one.
But shoppers who are medically exempt, for example if they have a lung condition, will still be able to shop without one.
The supermarket couldn't say if shoppers face being turned away if they refuse to wear a mask, but it told The Sun that it would still be down to the police to issue fines.
It'll be up to door marshals to ask customers to wear a face mask.
In some cases, shoppers may also be provided with a mask for free - for example, if they don't have enough money on them.
A pack of four Preema disposable face masks from Asda costs £2.80.
In line with government rules, the supermarket also confirmed that staff will be required to wear masks unless they're exempt.
Businesses who don't comply with the government rules could be fined up to £10,000.
1,000 new door marshals
To help ensure Covid rules are being following, Asda will bring in 1,000 new safety marshals.
These marshals will be placed at the front of stores and down the aisles of larger shops.
As well as being in charge of making sure people wear face masks, they'll also control the number of people in store.
We've asked Asda if they've hired more people to cover these marshal roles and we'll update this story when we know more.
Protective coating on baskets and trolleys
Asda is applying an antimicrobial coating to all its baskets and trolley handles to help stop the spread of viruses.
The same coating technology, known as Bio Master X shield, is already used to kill bacteria and viruses in the NHS Nightingale Excel hospital.
We've asked Asda how often it'll apply this coating and we'll be updating this story.
Additional hand sanitiser stations
Asda says it will be increasing the number of hand sanitiser stations in stores.
It already has sanitisation stands at the entrance at exits of its shops.
But the supermarket will bring in additional cleaning units in the busiest parts of its stores.
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