Greenpeace activists who scaled Parliament's roof and holed up for 10 hours say they felt forced to take illegal action because conventional lobbying had fallen on deaf ears.
Four climate change protesters - Johno Smith, Jeff Harrison, Abi Smith and Verena Maeder - face maximum sentences of three months in jail after being arrested for trespassing last night.
Their protest, which began before dawn, sparked an immediate review of security and raised concerns among some MPs about the ease of access to the Parliament complex.
Security was tightened at the Beehive and surrounding buildings in October after an attack on Canada's Parliament, but some of the measures have now been relaxed. The activists, some of whom were trained climbers and arborists, were aided by scaffolding which is surrounding the Parliament Building's exterior.
New Zealand First leader Winston Peters said it raised questions about whether security could prevent a terrorist act.
Act Party leader David Seymour said the activists were "arrogant and conceited" because protests should be made through "rational argument and explanation" and not stunts.
Greenpeace's chief policy adviser Nathan Argent said the lobby group, along with other NGOs, had attempted more conventional lobbying on climate issues, such as in a meeting with Prime Minister John Key two months ago.
But he said the National-led Government had not introduced a single policy to reduce greenhouse gas emissions in seven years.
"Taking the action we have today was borne of frustration because the message simply isn't getting across to politicians," Mr Argent said.
The protest was also a matter of timing, he said. The world was moving quickly to low-carbon economies, potentially leaving New Zealand behind. And critical climate talks were being held in Paris in December, at which New Zealand would be expected to raise its commitment to cut atmosphere-warming emissions.
Environment Minister Nick Smith defended National's record on climate change in the House yesterday.
"We introduced an emissions trading scheme in 2009, we joined the Global Research Alliance on Agricultural Greenhouse Gases, and we reversed the decline in renewable electricity from the previous Government.
"I would also note, with our Pacific friends in the House, the $100 million that our Government has invested there in providing them with clean and affordable energy."
Inspector Tony Bernards defended the decision not to remove the activists from the roof, saying it was the safest response.