Single-use plastic carrier bags will be phased out of all South Island Countdown stores from early October.
The supermarket chain is adding 67 stores to its countrywide phase-out from October 8, including 15 in Christchurch.
The move meant 85 per cent of the company's 180 stores would no longer offer the bags, as part of an aim to have all stores join in by the end of 2018.
Countdown's general manager of corporate affairs and sustainability Kiri Hannifin said their stores used an average of 6000 bags every day.
"The faster we can make this change, the sooner we can make a difference for the environment."