BEIJING - Despite a four-year ban on the practice, a report carried in Friday's edition of the Beijing Times indicated that many vendors are still giving free plastic bags to their customers.

Research by a civil investigation group showed that about 90 percent of?open markets still provide their customers with free plastic bags, despite the fact that markets, department stores and other retailers have been required to charge for the bags since June 1, 2008, the report said.

Research conducted by a Xinhua reporter found that the ban has been effective in supermarkets and department stores, while?open markets and other smaller vendors still give away plastic bags frequently.

Statistics from the National Development and Reform Commission show that in the first three years of the ban, the use of plastic bags in major retail locations decreased by more than 24 billion bags annually, equivalent to 200,000 tonnes of plastic.

Saving that much plastic also meant saving 3.6 million tonnes of crude oil or five million tonnes of coal equivalent, reducing carbon dioxide emissions by more than 10 million tonnes, according to the statistics.

However, a failure to fully enforce the ban means the actual emission reduction amount is likely much smaller.

Experts said the ingrained habit of depending on free plastic bags is one reason for their continued use at?open markets, as well as customers' desire to save money.

Gu Xiaoming, a professor at Fudan University, said the government should work to make the public more aware of emission reduction efforts and transform their consumption habits, adding that relevant supervisory departments should improve their efforts to enforce the ban.