This story was amended on August 27 to add comment from Foodstuffs.
Kiwis are being urged to look closely at their grocery bills and report any unexplained price increases.
It comes after complaints about supermarket lockdown prices rising in the past week.
Sam Pihema buys the same items at the same Countdown, twice a week - and insists prices have gone up.
He's feeding a family of six while on the benefit and says this week's grocery bill is the highest ever.
"It was over by $24," he said.
It's a feeling shared by others Newshub spoke to.
"Overall I think it has gone up," one said.
"Some of the meat has gone up," said another.
"I just bought not a lot of stuff and it came to $50, so [it's] definitely gone up a bit," a third person added.
In last year's alert level 4 Foodstuffs, which operates Pak'nSave and New World, and Countdown reduced their promotions and shoppers reported price increases across all main supermarkets.
Consumer NZ wants to know if it's happening again - and has launched an online survey for shoppers.
"They really are taking advantage of New Zealanders at a time they are vulnerable," Consumer NZ chief executive Jon Duffy said.
"There's a real moral question [that] supermarkets need to answer."
A photo from a customer showing flour bought on the first day of level 4 last week, and the same item from the same supermarket four days later - with a 74 percent price hike.
Since the story went to air Foodstuffs contacted Newshub and said the bakers worked out the wrong price per kilo and last week customers were actually buying flour at a price below what it was costing the store to buy it.
Once the store realised they corrected the price.
The Government's Price Watch website has also received complaints about grocery prices this lockdown - and is monitoring the situation.
"I'm told there's been 34 registers of concern to date - an average of four a day," Consumer Affairs Minister David Clark said.
But Foodstuffs and Countdown insist they haven't put prices up since lockdown started and that promotions are running as scheduled.
However, not all customers are convinced.
"There's not a lot on special" one customer told Newshub.
Foodstuffs said in a statement if a customer can’t find an advertised special in the store, this could be due to a number of factors.
"The uptick in demand, our ability to replenish due to the physical distancing measures in place, or in some cases, where we have prioritised the delivery of essential items to the store, over non-essential products that are on special".
Foodstuffs said prices can fluctuate depending on their availability, especially if it’s a seasonal product.
People who are faced with an unexplained price hike at checkout are being urged to report it to Consumer NZ.