Prime Minister Jacinda Ardern has committed the government and the public sector to go carbon-neutral by 2025, as she declared a climate emergency.

Ardern had moved a motion in Parliament this afternoon which would see New Zealand join 32 other nations in formally acknowledging the global crisis.

The motion was passed shortly before 4 p.m. with Labour, the Greens and te Pati Maori all voting in support, and National and ACT opposed.

It includes a promise to set an example by reducing its own waste and emissions.

"[Parliament will] show leadership and demonstrate what is possible to other sectors of the New Zealand economy by reducing the government's own emissions and becoming a carbon-neutral government by 2025."

Ardern also launched an initiative requiring the public sector to achieve carbon neutrality by 2025.

"Government agencies will have to measure and reduce their emissions and offset what they can't in order to achieve carbon neutrality.

"The public sector needs to be and will be an exemplar that sets the standard we all need to achieve by 2050," Ardern said.

The programme also includes an immediate focus on phasing out the largest and most active coal boilers, a requirement for government agencies to purchase electric vehicles and reduce the size of their car fleet, and for a green standard for public sector buildings.

Climate Change Minister James Shaw Photo: RNZ / Samuel Rillstone

It is backed by the $200 million State Sector Decarbonisation Fund.

"This policy, alongside today's declaration of a climate emergency, serves as a message to the public sector to get our own house in order. It's also a call to action for the private sector and it's great to see so many examples of businesses taking steps to reduce their emissions," Ardern said.

Climate Minister James Shaw said this builds on the progress the government has made over the last three years.

"In our first term, we put in place one of the world's most ambitious frameworks for reducing emissions, including becoming one of the only countries in the world to put in place a legally binding requirement to stay within the threshold of 1.5 degrees of global warming above pre-industrial levels.

"Now we intend to lead by example by measuring and reporting emissions across government, upgrading to cleaner sources of energy, cutting emissions from transport, and improving the efficiency of our buildings," Shaw said.

The climate emergency declaration notes the "devastating impact" that volatile weather will have on New Zealand, as well as the "alarming trend in species decline".

"Climate change is one of the greatest challenges of our time," the motion says.

National and ACT have dismissed the move as a marketing stunt, a criticism which is likely to prompt some concrete action alongside the symbolic gesture.

Efforts to declare a climate emergency last term were stymied with NZ First, National and ACT standing in opposition.

National leader Judith Collins said earlier today that it gives the public a false impression that there are substantial plans to tackle climate change.