NSW 'should ban' single-use plastic bags

The NSW government is being urged to join other states and territories in banning single-use plastic bags.

South Australia, Tasmania, the Northern Territory and ACT have already "banned the bag" and Queensland's ban will come into effect in July 2018.

"The NSW government is lagging behind other states and territories in taking action on plastic pollution and banning single-use plastic bags," Greens marine spokesman Justin Field said in a statement on Friday.

He said an estimated four billion light-weight plastic bags are used in Australia each year with about 50 million ending up as litter in the environment.

Most end up in waterways and the ocean "where they kill and injure dolphins, turtles and other marine life," he said.

A spokesperson for NSW Environment Minister Gabrielle Upton told AAP "the NSW government is looking at ways to reduce the impact of plastic bags including impacts associated with biodegradable bags".

People are being encouraged to refuse single-use plastic throughout the Plastic Free July campaign.