A checkout staff member told Checkpoint there have been daily tears, racial abuse and - in some cases - violence.
Customers have been warned repeatedly against stockpiling, but some shoppers continue to hoard essential items, at times leaving shelves bare.
Supermarket staff - essential workers - are being abused while struggling to keep up with the overwhelming demand of restocking shelves.
"I've had a few bad experiences since COVID-19 came to New Zealand," the checkout supervisor, who wishes to remain anonymous, said.
She said she was looking after her own children and her father. Her partner is also an essential worker.
"We've had people throwing things at us, spitting at us, swearing at us, putting us down, calling us names, being racist to us as well.
"I had a male come in… he threw a basket at me because there was nothing on the shelf.
"He said to me 'why the f*** haven't you got stock on the shelf, you should have the stock on the shelf'.
"And I went home crying that day... I felt like I didn't get any support from anybody… I started crying right there in the middle of all the customers. One customer did come up to me and said that I handled it really well.
"She said she was so grateful for our work that we've been doing.
"But it puts a lot of weight on our shoulders as workers ... because we're going there to provide for the community and our family, but we're risking ourselves getting abused.
"I literally cried to my partner and said 'I can't do this anymore'. I felt like giving up so many times."
The supermarket checkout supervisor said seeing staff members crying was a daily occurrence - for many different reasons, but mostly from being abused.
She said there were good customers who are made good comments, but attacks and other bad behaviour had increased.
"We are just trying to do our job."
Staff are often harassed for not wearing masks or gloves, but the Ministry of Health has said supermarket staff are not required to wear such personal protective equipment.
Supermarket staff can wear masks and gloves if it makes them feel safer, but they have to supply their own.
The checkout supervisor told Checkpoint it was the employer's responsibility to make sure employees feel safe at work.
"And if it means they need masks and gloves to make you feel safe at work I feel we should get supplied those."
She said currently she does not feel safe at work because of bad customer behaviour.
"I don't feel safe mentally. I don't feel safe in regards to my health.
"I have a father I care for - he's of very high risk to COVID-19. If I was to get the virus and bring it home, he'll be more likely to catch it and possibly die from it.
"A lot of us do have families at home," she said.
She said her store manager has been good but she would like to see more support from her company and the Government.
She would like to see supermarket workers getting the same treatment as healthcare staff.
"We serve hundreds of people a day. One operator - hundreds of customers, you could get anything."
Being a mother at the same time is very stressful, she said, as she does home schooling with her children after work. Her partner is also an essential worker.
She said her children and colleagues were what kept her returning to work each day.
"If we are going to do it, we are going to fight this together in our community."
Staff simply could not keep up with restocking supermarket shelves, she said.
"It's so hard to even just get a break. We've gone four hours, five hours without breaks, at a time, and there are workers working 12 hour shifts just to keep up."
Customers were continuing to buy up large on flour, tinned foods, long-life milk and meat, she said.
The Government has announced that supermarkets will close for Good Friday but be open for Easter Sunday.
The checkout supervisor said she was thankful that "people can have a break".
"All us workers deserve a break … Supermarkets should be closed on weekends, that's what I think.
"That's the kind of break we need to replenish our shelves. That break will be good for us to fill the shelves for all customers and community."
Her message for customers was simple: "Be kind. We're human too, and we're scared as well.
"That's what I want to say to all New Zealanders shopping in supermarkets. Be nice. Leave some for somebody else that may need it more than you do."
And what will she do with having Good Friday off?
"I'm going to sleep. I'm going to sleep and have a long bath."
In a statement, the company said the "level of abuse our team continues to face is incredibly concerning… taking frustrations out on supermarket staff is unacceptable".
On the issue of safety gear the supermarket said that even though the Ministry of Health guidance was that masks and gloves were not required, the company had ordered a shipment for staff that should arrive this week.
Safety processes were being peer reviewed by a third party, the supermarket said.