The government is pledging to rid the country of single-use plastic bags by July next year.

Prime Minister Jacinda Ardern and Associate Environment Minister Eugenie Sage have made the commitment at Wellington's Lyall Bay beach this morning.

Watch the announcement here:

This year 65,000 Kiwis signed a petition calling for an outright ban, and Ms Ardern said they were listening to those demands.

"Every year in New Zealand we use hundreds of millions of single-use plastic bags - a mountain of bags."

New Zealand is one of the highest producers of urban waste in the developed world, per capita, according to OECD data.

Photo: RNZ/Richard Tindiller

Ms Ardern said many plastic bags end up polluting the country's coastal and marine environments and cause serious harm to all kinds of marine life.

"And all of this when there are viable alternatives for consumers and business. It's great that many people are already changing the way they shop but it's important we take the time now to get this right."

She said before entering politics, and the prime minister role, she underestimated the impact of plastics on the environment.

"I also underestimated the strength of feeling amongst everyday New Zealanders around this issue. One of the groups of people that have helped me realise how much people care about plastics in the environment were children," she said.

"The biggest issue I get letters on from the public are about plastics and it comes from children. I literally get hundreds and hundreds."

"We in government have a role to play in the way we manage these kinds of issues and the way we respond to the public when they call upon us to address what might seem like a small issue."

Photo: RNZ / Richard Tindiller

Some of the children who wrote to Ms Ardern were invited to speak at the conference and said: "We all love the beach, it's New Zealand, we are basically a beach. But we are destroying our beach, we are littering our beach, it's become a dump. All sorts of fish are dying. We couldn't believe petone beach looked like that."

"I would like to tell you what I saw and what I found on the beach ... I was shocked ... it was sad to see how much plastic we found," another student said.

I think this is important because it's not fair for the animals that live in the sea. We are the ones letting plastics go into places where it could get into animals' stomachs."

Ms Sage wanted the public to give feedback on the best ways for this ban to be phased in - and has opened consultation until 14 September.

She wanted feedback on all aspects of the change, including options for the date the phase-out is to be complete by, what bags should be included, any retailers that should be exempted, and how best to help people with the transition.

"Public calls for action have encouraged a significant number of retailers, including supermarkets, to move on single-use plastic bags. We want to support their efforts by ensuring the retail industry moves together in a fair and effective way," she said.

Photo: RNZ / Richard Tindiller

Ms Sage the mandatory phase-out would be developed under the Waste Minismisation Act.

"The Waste Minismisation Act was groundbreaking when it was introduced in 2008, and today's announcemnet is part of this government's plan to use that act to its full potential... and to shift the economy to being a more productive and sustainable and inclusive economy."

She said that New Zealand, as a nation, needed to turn the tide on plastic pollution.

"Given our reputation for adapatability, the strong public call for action I'm confident we can make this change together and we can be proud of it."

Ms Ardern said the announcement and consultation process were just the beginning of change.

"This first five-week consultation is one of the first steps towards the government's longer-term plans to be smarter in how we manage waste."

Ms Sage said many countries and major cities around the world have successfully taken action on plastic pollution in recent years, and she was confident New Zealanders could also embrace the change.

Scientists also estimate that eight million tonnes of plastic enter the world's oceans every year, and if nothing changed, there could be more plastic in our oceans (by weight) than fish by the year 2050.

Recently 13 local and multi-national companies committed to use 100 percent reusable, recyclable or compostable packaging in their New Zealand operations by 2025 or earlier.

Retail NZ spokesperson Greg Haford told media at the conference that while in previous times there may have been backlash to change on plastics, customers now were more accepting.

"We know that retailers typically want to do the right thing by the environment and for their customers and it's true to say that customer views on plastic bags have changed very rapidly over recent times," he said

"[Retailers] have a huge opportunity to make a difference to the environment."

Photo: RNZ / Richard Tindiller

What you need to know about the mandatory phase-out plans:

Which bags does this ban include?

'Single-use plastic shopping bag' refers to those with handles commonly found at supermarket and other retail checkouts, and potentially thicker bags provided by some retailers.

As part of the consultation process, the government is looking into the maximum level of thickness that should be allowed.

The consultation document has more information on the different types of bags being considered.

Are biodegradable and compostable bags included in this consultation?

The proposed mandatory phase-out includes "biodegradable", "oxo-degradable" and "compostable" bags - all types of degradable plastics.

The government is recommending reusable bags over single-use alternatives for now because New Zealand does not yet have the nationwide infrastructure established to ensure that biodegradable and compostable plastics are processed in the right way.

Biodegradable and compostable plastics can be as harmful to nature as their non-biodegradable counterparts if they do not enter an environment that they are designed to break down in. Oxo-degradable bags break down into microplastics, rather than nutrients and materials which nature can absorb.

Why are you only consulting on a mandatory phase-out - why not a levy?

The government believes a mandatory phase-out is more effective and of less cost to the public as it can be done under existing legislation through regulations under the Waste Minimisation Act, whereas a levy or mandated charge would require new legislation.

It also said introducing a legislated levy or mandated charge over the top of supermarkets taking recent action to ban plastic bags would be inconsistent and create confusion.

How will I get my shopping home if I forget my bags?