Trade union Usdaw has claimed that plans to scrap Covid-19 rules could expose shop workers to infection and abuse.
From July 19, virtually all legal restrictions in England will be lifted.
General secretary Paddy Lillis argued there was “no reason” for the government to relax social distancing or mask laws.
“Many retail workers are at a greater risk of catching the virus and bringing it home to their families,” he said.
“Wearing a face covering in crowded public areas like shops is not merely a personal choice, it is an important measure to help protect workers.”
A study last year found that supermarket staff with “customer-facing” roles were five times more likely to catch Covid-19 than their colleagues.
Although shops can introduce their own restrictions, Lillis said the lack of legal backing would put employees at risk.
“Shop workers already face violence and abuse when enforcing these measures,” he continued.
“We are concerned that, when restrictions no longer have the force of the law behind them, this could result in further abuse, threats and violence.”
According to an Association of Convenience Stores report, Covid-19 regulations were the second most common trigger for assaults in shops.
One business, giving evidence to the Home Affairs select committee, blamed its sevenfold rise in violence to social distancing rules.
The news comes after British Retail Consortium head Helen Dickinson warned last week that easing restrictions could spark abuse and leave staff “in the firing line”.