The number of carrier bags in use in Northern Ireland fell by 26 million last year, it has been revealed.
Major supermarkets have been encouraging customers to take in reusable versions to save waste. The single-use bags end up in landfill and take years to decay.
Environment Minister Alex Attwood has launched a public consultation seeking views on charging for the throw-away carriers. "I fully acknowledge and welcome the success of voluntary efforts in reducing the number of bags in circulation," he said.
"In Northern Ireland, even with a sales growth since 2006 of more than four times the UK average, the number of bags handed out by major supermarkets in 2010 fell by 13.8% from the previous year. This equates to 26 million fewer bags in circulation."
He said 163 million carrier bags were issued by major supermarkets in Northern Ireland during 2010 and millions more were given out by smaller retailers.
"The introduction of a bag charge will build on the good work already under way, by helping to reinforce behavioural change. Customers will either have to pay the levy or bring their own reusable bags, thus reducing the amount of carrier bags ending up in landfill."
Average bag usage per person per month is slightly lower in Northern Ireland than in the rest of the UK. The total of 163 million in 2010 compared to 189 million in the 2009/10 financial year.
Director of the Northern Ireland Retail Consortium Jane Bevis said: "The proposed bag tax doesn't support the environmental efforts of retailers and their customers. Instead it penalises businesses and consumers during a difficult financial period.
"This contradictory levy will drive up the cost of getting shopping home without significantly contributing to green efforts or government coffers and should be abandoned."
A total of 6.8 billion carrier bags, including single-use, bags-for-life and reusable bags such as those made from cotton and jute, were used by supermarket customers across the UK in 2010.