Chambers said customers adapted quickly.
"We're confident Kiwis will get in behind this change across the country, and we're committed to making the move from check-out bags as simple for customers as we can."
Charging customers for plastic bags was considered, but rejected, Chambers said.
"Charging is also not the ideal outcome for the environment, because these bags are still provided," Chambers said.
Over the coming months, more affordable and sustainable initiatives will be introduced, including permanently reducing their reusable bags from $1.39 to $1 from October 9.
The plastic bag target will become a key part of Countdown's efforts on waste minimisation, which already includes Countdown's target to producing zero food waste.
Auckland Mayor Phil Goff said charging for or banning plastic bags could not be introduced through a council bylaw and he would continue to work with MPs to promote a change through a local bill in Parliament.
"I met with Countdown early in my mayoralty to seek their support for reducing plastic bags in Auckland. It is great to see them responding positively to our discussion and to customer sentiment.
"Reducing plastic bag use is a crucial part of decreasing waste and protecting our environment. I encourage others to follow suit.
"If other businesses make efforts to reduce plastic bag use and the Government introduces a levy on plastic bags, we can likely cut around 500 to 600 million plastic bags a year out of our waste stream in Auckland alone."
Greenpeace is also offering high praise to Countdown for the plan to eliminate single-use plastic bags from its supermarkets.
"Massive props to Countdown today. They've taken a bold move that makes them leader of the pack on plastic reduction," says Greenpeace spokeswoman Elena Di Palma.
"They've realised how strongly the New Zealand public sees these bags as pure environmental craziness."
Rival supermarket New World are polling customers asking whether they want to pay a charge for single use bags, something Greenpeace has criticised as a weak measure