Almost every shop worker asked in a recent survey said they have experienced verbal abuse.
The survey also found that 70% said they had been threatened by a customer, and 14% had been assaulted.
The findings come as the retail trade union Usdaw renewed its call for a new protection of workers law.
Nearly 2,000 retail staff across the UK were surveyed, and 92% said that in the last 12 months they have experienced verbal abuse.
One in five victims said they had never reported an incident to their employer, including 5% who had been assaulted.
Some of the comments in the survey from Northern Irish shop workers included one who outlined: "People throwing things at me, being abusive about waiting times and about not wearing masks".
Another said they had been called names and sexually harassed, while another worker said they had been physically slapped by a customer, spat at and had groceries thrown at them.
Usdaw general secretary Paddy Lillis described the testimonies as "heart breaking", adding the workers "deserve far more respect than they receive".
"Our latest survey results clearly show the scale of the appalling violence, threats and abuse faced by and demonstrate the need for a 'protection of shop workers' law," he said.
"It has been a terrible year for our members, with over 90% of shop workers suffering abuse, more than two-thirds threatened and one in seven assaulted.
"We are saying loud and clear that enough is enough, abuse should never be part of the job.
At a time when we should all be working together to get through this crisis, it is a disgrace that staff working to keep food on the shelves and the shop safe for customers are being abused. Action to protect shop workers is needed.
"Today a new protection of shop workers law comes into force in Scotland, but we are deeply disappointed that the UK Government has continued to resist a similar measure in England, Wales and Northern Ireland.
"Retail staff across the UK have a crucial role in our communities and that role must be valued and respected, they deserve the protection of the law.
"This is a hugely important issue for our members. They are deeply concerned that the current high levels of abuse will become the norm, unless the Government takes urgent and meaningful action."