Shoppers at a South Auckland supermarket say mice have been running wild in the store for up to a year.
Countdown in Takanini says it has spent more than $20,000 "to move fittings and prevent mouse access".
But upset shoppers say they will not shop at the store again until it gets rid of the vermin.
A Manurewa mother, who declined to be named, said she saw several mice run from one aisle to another just before 10am yesterday.
"At first I thought I was dreaming and then I saw it again," she said.
"Then we went to the bread aisle and we saw two, one from underneath the bread."
She asked to speak to the duty manager and said the woman who responded said, "Oh, we know we have a problem, we're trying to fix it, but it's not going away."
She posted about it on the Facebook group Manurewa Spread the News and got "heaps and heaps of responses".
"Other people said they saw it when they were there as well and they are not shopping there again," she said. "I'm not shopping there - no way!"
One person, Diana Valkenborg, posted: "They have had a mouse problem for over a year now. I could smell it in the aisle across from info desk."
Valkenborg told the Herald she recognised the smell because she used to keep mice.
"It smelt like a couple of male mice living in there. Male mice smell way worse than females," she said.
"It was just in that particular bay, at least a year ago."
Randwick Park Community House manager Jean Areaiiti posted: "I've seen mice run from under the shelf in one aisle at this same store over a year ago."
Teahiiti Cataleeya Haki Davey posted: "I saw exactly the same when I went there one night ... I just didn't know what to say, like omgoshhh ... disgusting."
However, others were understanding. One person commented: "The cold wet weather is bringing them in plus there is the vacant land behind them. Would be hard to keep the little blighters out I would think."
Another wrote: "I'm sure every shop has this problem, they get in anywhere."
The first shopper said she rang Auckland Council about it.
"If this was a restaurant it would be closed down straight away," she said.
But a council spokeswoman said the council only regulated cafes and restaurants, and shops were regulated by the Ministry for Primary Industries (MPI).
MPI said it had received a complaint about the mice and was following up with the affected supermarket.
A Countdown spokeswoman said the store manager "immediately contacted Rentokil to come in when the customer contacted us to let us know about the mice sightings".
"We take pest control really seriously and work with specialists like Rentokil to monitor and address any pest activity that we come across in our stores," she said.
"In cooler months mice tend to look for warmer environments and we think this is what's happening in Takanini at the moment.
"In response, we've increased Rentokil's visits and are continuing to regularly clean the store throughout the day as well.
"We've experienced mice activity in the past at Takanini and have invested more than $20,000 to move fittings and prevent mouse access. We'll continue to monitor and take measures to deter mice from our store."