Having worked in retail for four years while at school and university, Mr Burrows, 19, said his experience of serving customers had been positive on the whole.

But more recently, after apologising to one customer for being unable to serve him after trading hours, he was shocked at the response.

"He wasn't happy about that and went into a tirade of abuse and just spat on me," Mr Burrows said.

The Shop Distributive and Allied Employees' Association, which represents retail and fast food workers, will on Monday release the results of a national survey of 6000 of its members which has found almost half – 44.4 per cent – have been physically or verbally abused by a customer.

In response to the growing problem of abuse, the union is launching a campaign to call on customers to "keep your cool" with retail workers.

SDA National Secretary Gerard Dwyer said it was not acceptable for thousands of retail and fast food workers to be abused at work.

"Customers need to be reminded that shops are also workplaces," Mr Dwyer said.

The campaign will promote messages including: "Customer abuse is not part of the job" and "Respect".

During his early days on the job, Mr Burrows found customers could become angry and shout if cleaning products were put in the same shopping bag with food items, such as bread.

But more recently, as he has moved into senior management roles, Mr Burrows has dealt with more serious abuse.

One customer who tried to get a refund on items without a receipt became angry when Mr Burrows offered to look for an electronic record of the purchase.

The customer started swearing and stormed out of the store only to return with a glass bottle that he threw and smashed near Mr Burrows.

"Ten minutes later he came back holding a glass bottle of vitamins and threw it at the service desk and started abusing us and threatening physical assault," he said.

Another colleague was punched in the stomach when she asked to search a customer's bag.

Dale Greenup, who has worked for a supermarket in Tweed Heads for 19 years, said abuse from customers had increased in recent years.

"I've found in the last few years it is definitely getting worse up here," he said.

"I put it down to a lot of people who are homeless.

"A lot of people are alcohol or drug affected and they come in aggressive."

A month ago, one customer pulled a knife on Mr Greenup and a colleague shortly after the supermarket opened for the morning.

Another staff member had noticed a woman shoplifting and when confronted, the customer threatened them with a sharp blade.

The police were called and the woman was arrested.

A week ago, another customer started yelling abuse at staff when confronted with unpaid items taken from the store.

"He started getting abusive and yelling," Mr Greenup said.

"We get abuse all the time – especially the girls at the front end of the shop."

SDA NSW Secretary Bernie Smith said the problem of verbal and physical abuse from customers was a growing problem.

"The constant verbal abuse really gets to people over time," he said.

"There needs to be zero tolerance for that kind of behaviour."