The change, which makes it harder for shoppers to find the cheapest item, quietly happened on New World and Pak'n Save's websites in early October.
Both supermarket chains are owned by Foodstuffs NZ.
One shopper RNZ spoke to called the move "a silly thing to do".
"Any information that helps people make comparisons is absolutely vital. It tells customers that they're they want to obscure what they're doing."
Another said she thought it was "quite dodgy behaviour."
"Oh no, I don't agree with that."
A third said it was "cheeky" and "kind of annoying" for online shoppers searching for a no-frills option.
"Say you want a kg of sugar, you'll, you'll sort by the cheapest one, because you don't really care. It's just sugar."
Consumer NZ spokesperson Sahar Lone told Checkpoint the move was "bizarre" given the current the economic climate.
"The key competitor to Foodstuffs (Woolworths) has made their tool for sorting by price more prominent. So it seems unusual... [to] remove it altogether."
Although the "sort by price" option is still available on the supermarkets apps, their websites only allow items to be sorted by popularity.
"But really, that doesn't help you," to find the cheapest item, she said.
Users can also choose to display only those items on special. A feature that often pushes the supermarket's own brand to the top of the page, said Lone.
"What we've observed based on, you know, running general tests for items like milk and bread, is that what does tend to be served up is Pams.
"Rather than the cheaper products, you know, or products that are made by local suppliers.
"The supermarkets are essentially clipping the ticket twice," she said.
However, Lone stressed Consumer NZ had not run "comprehensive investigations" to determine whether or not online shoppers were being force-fed the supermarkets' inhouse brands.
"But it does appear that a lot of them are served up in the first few results if you run searches.
"What [Foodstuffs] told us is that what is served up is based on either if you're logged in, it's based on your past behaviour, or if you're not logged in, it's based on what other people in your region are searching for.
"That might be true, but really we have no transparency."
Lone said the move was "really surprising" given the recent Commerce Commission scrutiny directed towards Foodstuffs and a Consumer NZ report finding the cost of groceries was shoppers biggest concern.
"We don't believe, you know, it's, it's kind of a natural way for a supermarket to behave right now."
In a statement, Foodstuffs said it was upgrading its digital platform and improving its e-commerce offering with more transparent unit pricing.
"Soon, we'll add a new sort feature allowing customers to sort products by price or unit price.
"We're aiming to have our new price sorting tool live within our PAK'nSAVE and New World websites by mid-November. Meanwhile, customers using our PAK'nSAVE and New World apps continue to have the option to sort their search results by price.
"Our goal is to make finding products online quick and convenient, whether customers are searching or browsing categories.
"In the interim, there is still the 'sort by' feature available to use within the app."
