A plastic bag ban has prompted some Dunedin shoppers to walk out of a supermarket's grounds taking shopping baskets and trolleys with them.

Countdown supermarkets in Dunedin and Mosgiel stopped using single-use plastic carry bags on August 13, responding to concerns about the effect of plastics on the environment.

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Responding to a query from the Otago Daily Times, Countdown Dunedin Central store manager Ron Andrew said baskets had been going missing, and his team planned to collect any trolleys and baskets left in the street.

"We've seen some baskets go missing this week, which is of course a little disappointing, but we also understand that sometimes behaviour change can be tough."

Andrew said he planned to do reusable bag giveaways in the North Dunedin area to help university students "build their collection".

People who brought back a basket would be given a reusable bag in return, "no questions asked".

Andrew said on the whole his store had had "a great response from customers", most of whom were bringing reusable bags when doing their shopping.

The customer reaction follows the Government's plan to phase out single-use plastic bags over the next 12 months.

Prime Minister Jacinda Arden has said: "We're phasing-out single-use plastic bags so we can better look after our environment and safeguard New Zealand's clean, green reputation.

"Every year in New Zealand we use hundreds of millions of single-use plastic bags – a mountain of bags, many of which end up polluting our precious coastal and marine environments and cause serious harm to all kinds of marine life, and all of this when there are viable alternatives for consumers and business."

Ardern said the Government had listened to the 65,000 New Zealanders who had this year called for the ban through a signed petition.

"It's great that many people are already changing the way they shop. But it's important we take the time now to get this right so we can help all New Zealanders adjust their shopping habits," she said.

"We need to be far smarter in the way we manage waste, and this is a good start."