Lidl, Iceland and the Co-op have been named the UK's least Covid-safe supermarkets, despite traffic light systems and one-way queues to help manage overcrowding in stores.
'Big four' grocer Asda also fared poorly, with shoppers complaining that there are "too many people, no one-way system...and too many shoppers without masks" in stores.
Supermarkets have remained open throughout the pandemic along with post offices, hardware stores and banks.
But under essential retailer guidelines, they must be Covid-safe, meaning checkout screens, limits on the number of people allowed in stores and floor markings for social distancing must be in place.
However, watchdog Which? Said despite their best efforts, just two in five shoppers feel safe in stores.
The group asked 2,010 members of the public how they have felt about supermarket shopping during the third national lockdown.
Only 38% said they felt safe.
Just two-thirds of Lidl and Iceland customers rated the supermarkets' measures as good or excellent.
A Lidl customer complained the aisles were too "narrow to easily social distance," while an Iceland customer said there was a "distinct lack of sanitising products when entering the store."
Lidl said in a statement that the health and safety of its colleagues and customers "remained our top priority."
The supermarket said it reminds customers about face coverings and has floor markers to encourage social distancing as well as dedicated sanitising stations and checkout screens.
Iceland said the Which? findings were based on a relatively small sample, and not representative of the feedback it has had.
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A spokesperson said: "We have invested heavily in making our stores as safe as possible throughout the pandemic, continuing to update our policies and safety measures in line with government guidelines."
One Co-op customer said there were "too many people allowed in store and no enforcement of the one way aisle system."
An Asda customer also complained that there were "too many people in-store, no one-way system ...and too many people without masks."
A Co-op spokesperson said: "Keeping our colleagues and customers safe is our top priority and we have introduced clear social distancing measures to protect everyone in our stores, in line with government advice.
"Traffic light entry systems, protective screens, face coverings, one-way systems, floor markers and hand gels have been implemented throughout the pandemic, with 92% of shoppers happy with these measures."
Shoppers ranked Sainsbury's as the most Covid-safe, with eight in 10 customers rating its procedures as good or excellent.
One customer explained that they "feel generally safe, as the store is spacious and the option of self-serve with screens is good."
Sainsbury’s was closely followed by Waitrose and M&S, with 78% and 79% of customers respectively rating their Covid-safety measures highly.
