Shop bosses have warned staff to turn a blind eye if customers refuse to wear face masks over fears they risk being assaulted.
Stores will tell shoppers that coverings are compulsory from tomorrow.
But the Association of Convenience Stores said: “We have advised members not to challenge customers unwilling to wear a covering.”
Police warn officers should only be called as a “last resort”.
There are growing concerns over how Prime Minister Boris Johnson’s mandatory face mask rules in stores would be enforced without putting frontline staff at risk.
While supermarkets have indicated they will advise customers that the mouth and nose coverings are a must-wear from Friday, there was still a massive muddle over how to impose the rules.
Most said they were taking a softly-softly approach with posters at store entrances reminding shoppers it was compulsory to wear a face mask but without any heavy handed actions to back it up.
Britain’s biggest grocer Tesco said it will also have face mask stands at entrances so forgetful shoppers can take and open a pack, put one on and pay at the checkout but there was no enforcement policy.
Sainsbury’s revealed it would not “challenge customers” in its aisles as it was worried “they may have a reason not to wear a mask”.
And the Co-op followed suit and said its staff would not question those without masks but added: “It is the responsibility of all non-exempt customers to ensure they are in adherence with the new legal requirements.”
The Association of Convenience Stores (ACS) said it has urged its 33,500 members to turn a blind eye to those who don’t comply as it was concerned about repercussions.
Its chief executive James Lowman said: “We are helping retailers to communicate the rules around face coverings as widely as possible to customers, but have advised our members not to challenge customers who are unwilling to wear a face covering.
“The safety of retailers and their colleagues is our number one priority and we are keen to avoid any potential flashpoints of abuse in stores.”
The organisation is issuing posters with the words “thank you for wearing a face mask” along with signs explaining why some members of staff and customers may be mask free.
Its figures show a 40% rise in the number of verbal and physical assaults on shop workers since lockdown began.
The British Retail Consortium (BRC) also said the safety of staff and customers was a priority.
BRC chief executive Helen Dickinson said: “While retailers will play their part in communicating the new rules on face coverings, they must not be the ones enforcing these rules.
“With hundreds of incidents of violence and abuse directed at retail staff every day, we welcome the announcement that enforcement will be left to the authorities, rather than potentially putting hardworking retail colleagues in harm’s way.”
But confusion still reigns over the industry as shopping malls and takeaways are still waiting for government guidance on how the new rules affect them.
They will finally be told today (Thursday) – just 24 hours before face coverings become mandatory giving them little time to implement the rules.
One retail insider said: “There is no clarity but plenty of frustration as everyone is waiting for the criteria to be published. It’s been left a little late.”
And it’s hardly surprising why retailers and shoppers are unclear if it’s masks on or off when buying food-to-go as even government ministers have sent out mixed messages.
For just last week Cabinet Office Minister Michael Gove popped into a Pret a Manger in Westminster to pick up his lunch maskless while trade secretary Liz Truss bought her lunch wearing a face covering, only for Mr Gove to do U-turn and don a mask for a trip to Pret this week.
No wonder the retail industry is keeping its fingers crossed that the confusion will be cleared up today when the criteria for where face masks are mandatory is eventually revealed.
Yesterday, Britain’s top cop, the Met’s Dame Cressida Dick further fuelled the debate over who was going to be the face mask enforcer by urging shops to only call officers to stores “as a last resort”.
She said while she hoped most people would follow the face mask rule, those who ignored it would be “shamed into complying or shamed to leave the store by the store keepers or by other members of the public.”
The Metropolitan Police Commissioner told LBC: “Calling the police should be a last resort for dealing with a mask issue. But of course the law is the law.
“If somebody is concerned about what is going on in their store, yes, of course they should call the police and we will try to assist.”
Andy Marsh, chief constable of Avon and Somerset Police, told a Facebook Live session his force has “very limited capacity” to enforce the rules,
and would only have a role in “a tiny minority” of cases”.
He said: “It certainly won’t be the case that we will be encouraging people to call us if you see someone not wearing a face mask. And I can’t offer any assurance that police officers will routinely be able to attend such incidents.”
And Thames Valley and Devon and Cornwall police forces said they would only attend if scenes turned violent.
Under the new face mask law, shops and supermarkets can refuse entry to people who are not wearing a face covering and police can issue £100 fines for a failure to comply.
A Department of Health and Social Care spokesperson said: “From Friday 24 July it will be mandatory to wear a face covering in shops and supermarkets, as is currently the case on public transport.
“If a shop or supermarket has a café or a seating area to eat and drink you can remove your face covering in that area.
“Further details will be set out in the regulations.”
What type of mask should I use?
Options include medical-grade respirators, disposable masks and scarf-type onQes with filteArs.
Public health consultant Maggi Morris says: “The highest-grade are & expensive and most are disposable.
“Lower-grade masks are also disposable. Cloth coverings need to be regularly washed.”
Can you share clean masks?
Martin McKee, Professor of European public health at the London School of Hygiene & Tropical Medicine, says: “Providing coverings have been properly washed, I see no reason why one might not be used by someone else in an emergency.”
What if I touch my mask?
Ms Morris says: “We know the virus can survive on a surface for hours if not days. So you need to wash your hands or sanitise, take it off and put on a replacement.”
Should I carry a spare mask?
“Yes,” says Ms Morris. “Keep one in something like a freezer bag to take in your bag or pocket.”
How do you stop your glasses steaming up?
Jeremy Howard of campaigners Masks4All says dip them in soapy water and let them dry. It creates an anti-fog layer on the lenses.
What about children?
Face coverings aren’t mandatory for under-11s – and under-threes must not wear them. Ms Morris warns: “Don’t buy the baby masks on the market.”