Banning the Bag. Jacinda Ardern announces a phasing out of plastic bags during a beach clean up at Lyall Bay.

Single-use plastic shopping bags are to be phased out over the next year, as the Government plans to crack down on the environmental villain.

Prime minister Jacinda Ardern and associate environment minister Eugenie Sage made the announcement at Lyall Bay, Wellington, on Friday morning.

"Every year in New Zealand we use hundreds of millions of single-use plastic bags – a mountain of bags, many of which end up polluting our precious coastal and marine environments and cause serious harm to all kinds of marine life," Ardern said.

"We're phasing-out single-use plastic bags so we can better look after our environment and safeguard New Zealand's clean, green reputation."

READ MORE:

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* Where a plastic bag can get you jailed

The PM said there were viable alternatives for consumers and business.

Last year, the Bags Not campaign was launched by Stuff to bring awareness to the problem and highlight public support behind action.

AMBER-LEIGH WOOLF/STUFF Prime Minister Jacinda Ardern has announced single-use plastic shopping bags will be phased out over the next year.

Ardern said plastic was the single biggest subject school children wrote to her about, and this year 65,000 New Zealanders signed a petition calling for an outright ban on bags.

Refusing to change would have meant there could be more plastic in the oceans by weight than fish by the year 2050, Ardern said.

The Government has released a consultation document to work out exactly what types of bags could be captured by the ban.

ALDEN WILLIAMS/STUFF Every year New Zealanders use hundreds of millions of single-use plastic bags.

BAN WILL 'PUNISH' CONSUMERS: ACT

But not everyone is pleased with the planned ban.

ACT Party leader David Seymour said the ban would "punish responsible consumers and may produce worse environmental outcomes."

"Plastic waste gets into the environment as it's collected and transported to landfills. This isn't the fault of Kiwis who find plastic bags easy and convenient and dispose of them responsibly."

Seymour also took aim at the Green Party: "No Green MP has a science degree, so it's not surprising that this policy could end up hurting the environment."

National Party leader Simon Bridges said the plastic bag ban was "low-hanging fruit that won't make any real difference".

He said the Ardern-led Government had bigger problems on its hands.

"The Prime Minister should turn her attention to fixing the very real concerns around plummeting business confidence and our slowing economy ."

Bridges said New Zealanders were already reducing their plastic bag use.

"They didn't need to be told what to do by a Government increasingly looking like it thinks it knows best."

CAMERON BURNELL/STUFF Associate environment minister Eugenie Sage says many countries and major cities around the world have successfully taken action on plastic pollution in recent years.

LONG ROAD TO CHANGE

A Greenpeace petition was launched in July last year and went to Parliament in February, but in 2014, a similar petition garnered only a quarter of the number of signatures.

Ministers had hinted at action earlier this year but remained quiet over committing to definite change.

On Friday Greenpeace said the ban was "a win for people power and the first big step towards addressing marine plastic pollution".

"This could be a major leap forward in turning the tide on ocean plastic pollution and an important first step in protecting marine life such as sea turtles and whales, from the growing plastic waste epidemic," said Emily Hunter, Oceans Campaigner at Greenpeace.

"In growing numbers over the last decade, New Zealanders have been calling for a ban on single use plastic bags. Today marks the beginning of the end for over 2 billion single-use plastic bags that clog our communities, coasts, rubbish dumps and oceans each year."

Hunter said the planned ban was a great first step, but more was needed.

The Packaging Forum, an industry group with a focus on recycling said a ban would set a level playing field for the retail industry, and to take an estimated 800 million bags out of circulation.

Soft Plastics Recycling Scheme manager Lyn Mayes said the primary goal of the forum was to reduce the amount of plastic packaging used.

Mayes says the Packaging Forum supports the inclusion of compostable and degradable plastics in the proposal.

"New Zealand does not yet have a standard for compostable packaging, nor does the current infrastructure take most of these products in the volumes presented, which means they will mostly end up in a landfill.

Retailers - such as Countdown, New World and most recently Mitre 10 and Z Energy - have already announced plans to phase out the bags.

New Zealand supermarkets are already removing plastic bags from checkouts, with Countdown phasing the bags out in ten stores already, with a plan to have no bags by the end of 2018.

New World announced similar plans, and a customer poll on bag charges revealed users would rather have a ban.

More than 40 countries across the world have already taken action, and Denmark has had a plastic bag levy since 1998.

In the United Kingdom levies have seen plastic bag use plummet by over 80 per cent, and using a plastic bag can even bring a jail sentence in Kenya.

Former PM Helen Clark has previously said New Zealand was well behind many countries that had already legislated against plastic bags.

SMARTER ON WASTE

Ardern said people were already changing the way they shop.

"But it's important we take the time now to get this right so we can help all New Zealanders adjust their shopping habits.

"We need to be far smarter in the way we manage waste and this is a good start."

The Government was determined to face up to New Zealand's environmental challenges, she said.

"Just like climate change, we're taking meaningful steps to reduce plastics pollution so we don't pass this problem to future generations."