The NSW government is being urged to ban single-use plastic shopping bags by the end of the year after Victoria acted on the issue earlier this week.
NSW may be the only state in Australia without a plastic bag ban, but Premier Gladys Berejiklian says she see's no point in taking action if big business already has.
Victorian Premier Daniel Andrews on Tuesday committed his state to joining South Australia, Western Australia, Tasmania, Queensland, Northern Territory and ACT in implementing a ban next year.
But Ms Berejiklian said on Wednesday she had no plans to ban the bag, given big supermarket chains were already phasing them out.
"I'm someone who believes that if it's happening anyway, why does government have to come in as well," Ms Berejiklian told reporters in Sydney.
According to Greenpeace Australia research, no government ban means 1.1 billion single-use bags not distributed by supermarkets will continue to be discarded in NSW each year.
"Letting supermarkets lead the state on environmental issues would be weak," Greenpeace's Simon Black said in a statement.
"The premier's inaction is disgraceful.
"That's billions of bags that Berejiklian is letting end up in our waterways and landfill."
NSW Opposition Leader Luke Foley also called for Ms Berejiklian to act.
"Not a single leader in the country agrees with her about plastic bags - and neither does the community," he said in a statement.
Ms Berejiklian said she was happy with how the private sector was managing the situation, but added she wouldn't be opposed to a national approach.