Single-use plastic shopping bags will be phased out over the next year, the Government has announced.

Prime Minister Jacinda Ardern and Associate Environment Minister Eugenie Sage made the announcement on Friday, proposing a six-month phase-out period.

The move will help look after the environment and safeguard New Zealand's clean, green reputation, Ms Ardern says.

"We're listening to New Zealanders who want us to take action on this problem. This year 65,000 Kiwis signed a petition calling for an outright ban."

It is the biggest single subject school children write to Ms Ardern about, she says.