Some supermarkets are now asking customers to leave their bags in the boot and pack groceries back at the car, in a further bid to stop the spread of coronavirus.
Foodstuffs said the recent policy change - which applied to New Worlds in the North Island - would speed up the checkout process and move customers through the stores faster.
"Customers are temporarily being asked not to pack their groceries into their reusable bags at checkout," head of corporate affairs Antoinette Laird said.
"Instead we ask shoppers to load their groceries back into the trolley and pack it into their bags at the car.
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"The main reason for this is to help customers move through the checkout process quicker, hence reducing the amount of time spent in-store – this in turn speeds up the process for everyone and allows us to significantly reduce customer queues outside stores."
Laird added it was very important to follow physical distancing instructions from the Government.
"The less time we spend with our fellow Kiwis right now the better. We appreciate this is challenging but it is important to follow this guidance so we can limit the spread of Covid-19."
At least one Pak'nSave - also part of Foodstuffs - is also requiring customers to pack their own bags, although the company says that's always been their policy.
A shopper at the Mt Albert Pak'nSave told the Herald when he arrived at the checkout on Saturday morning and opened his bags to help the operator pack them, she told him she was no longer allowed to pack customers' bags under a new policy.
"She then stacked my groceries in the trolley before I had to unstack them back into my bags once I was through the checkout," he said.
"After queuing for an hour or so with hundreds of others to get inside, this seemed like an exercise in double handling and time-wasting."
However, a Foodstuffs spokeswoman said the bag policy only applied to New Worlds.
"Customers always pack their own bags away from the checkout at Pak'nSave ... You pack, you save."
A spokeswoman for opposition supermarket chain Countdown said they were not seeing bottlenecks at the checkouts.
"We have very strict hygiene processes in place around our checkouts as well as a strong queue management system, which is designed to keep our team and customers safe," she said.
"In Countdown stores our checkouts are designed in a way that makes packing food and groceries very quick and easy, and we also have an option for customers to pack their groceries straight into their trolleys at the moment too.
"As always, we'd encourage customers to check their reusable bags are clean
when they shop with us."