The Greenpeace protestors abseiled down from Parliament and were arrested for trespass.

Four Greenpeace activists who scaled the roof of Parliament on Thursday in a climate change protest have been charged with trespassing.

Applause and toots of a bike greeted them as they made it down, one by one, around 5pm on Thursday.

The four had abseiled down onto a ledge at 6.30am on Thursday morning and put together a solar panel array and unfurled a banner criticising Prime Minister John Key on climate change.

STACEY KIRK / FAIRFAX NZ Police lead away one of the protesters that came down off the roof of Parliament.

The two men and two women were charged with trespass, which carries a maximum sentence of three months imprisonment, said Inspector Tony Bernards.

Police said around 6pm that the four had been released from police custody and would be summonsed to appear in court at a later date.

They have also been trespassed from Parliament.

STACEY KIRK / FAIRFAX NZ Two of the four protesters who climbed Parliament descend from the roof late on Thursday afternoon

There will be a full review by Parliamentary Security into how they group got up there. Police will carry out the criminal investigation.

Bernards said New Zealand welcomed protest , as long as it was lawful.

"This is unlawful protest - as a result we have arrested two males, two females for protest on the Parliamentary grounds."

ROSS GIBLIN/Dominion Post Climate change protesters scale Parliament to urge Prime Minister John Key to take action.

Bernards still did not know how the protesters had got onto the roof, and said the Speaker and Parliament security were investigating how it had occurred.

Having dealt with Greenpeace previously, Bernards said they were usually upfront about how long they would protest for, and Police had liaised with the protest organisers over their descent.

The protest had been "very, very dangerous", and the risk posed of arresting them from their position had been too high.

Jeff Harrison A selfie of Greenpeace protester Jeff Harrison.

Bernards did not know whether it was the biggest security breach in Parliament's history.

Earlier the protestors rolled up their sign of Prime Minister John Key that was emblazoned across the Government buildings.

They fed large solar panels they took with them through a top-floor window into Labour's communications unit to get them down.

'SERIOUS RISK'

Earlier, Speaker David Carter said the protesters posed posed a "serious risk" to Parliament.

The breach sparked a full review of security to be ordered by the head of Parliamentary Service, while Carter called for a report on how security was bypassed.

JO MOIR Two men and two women abseiled down onto a ledge and put together a solar panel array.

He said he didn't expect the scaffolding, in place for maintenance work on Parliament, to be a risk but "in hindsight we've got to be prepared for any of these sorts of attacks".

Twenty years ago protesters had installed solar panels, drawing attention to climate change, however, Carter said he thought Parliament's security had improved.

"It's a lot tougher".

'INCREDIBLY IMPORTANT'

Meanwhile, David Stevenson, general manager of Parliamentary Service, promised the protesters would be dealt with by police "as would any other trespassers".

Former Greenpeace worker and current Green MP Gareth Hughes said it would be fantastic to see solar panels installed on the Parliament buildings to save taxpayers money.

Hughes acknowledged the security breach was a concern, but he expected Greenpeace to stay peaceful during their non-violent protest.

The message from the protesters was "incredibly important".

"We've seen our emissions grow in New Zealand, we've seen a focus on drilling, fracking, mining - not taking up the tremendous opportunity to grow clean energy jobs - it's a very important message."

The Green Party supported the message behind the protest, and was calling for the Government to take a science-based target to the climate conference in Paris this year.

Deputy Prime Minister Bill English said he had paid the protest little attention.

"I haven't seen them, I don't know what they're saying and I don't think much of Parliament's paying them much notice," he said.

Jo Moir/Stuff.co.nz Four Greenpeace protesters got onto the roof of Parliament and put together a solar panel array.

"Of course they should come down. It's pretty dangerous up there. I hope they're keeping all the work place safety rules, otherwise they'll be prosecuted."

English did not expect the protest to be effective.

"Everyone can see it's a bit of a stunt. We don't really know what they're on about and most people will never see them."

The protest was about climate pollution "spiralling out of control" under the National Government, a Greenpeace spokeswoman said.

'DISAPPOINTING' NOTHING DONE

Greenpeace chief policy advisor Nathan Argent said it was disappointing that in two decades nothing had changed and protesters were back repeating what had been done 20 years ago, he said.

The protest was about showing the Government a plan was needed to take the pollution out of the economy.

"The Government over the last seven or eight years have done nothing. They haven't introduced a single policy to reduce emissions", he said.

The four protesters on the ledge were all trained climbers, some of them climbed professionally, Argent said.

The rest of the world was moving on climate change, and the protest was about sending a message to the Government and Prime Minister, he said.

The protest was criticised in a tweet from environmental group Forest and Bird.

"Climate change is a critical issue that requires action now, but we don't endorse today's breach of parliamentary security by protesters," the tweet said.

Green Party co-leader Metiria Turei said it was concerning that in two decades no action had been taken on climate action when the rest of the world was making progress.

"I'm really concerned about the security breach, but outside of that Greenpeace is representing thousands of New Zealanders who want action on climate change," Turei said.

PHOTO-SHOOT OFF

The Green Party has had a photo-shoot of their co-leaders ruined by a Greenpeace protest.

For weeks the Greens have been planning to get promotion shots of new co-leader James Shaw with co-leader Metiria Turei but their scheduling has now clashed with a protest on climate change.

Green Party chief of staff Andrew Campbell said it was a "pure coincidence" that the protest had taken place on the same day Carter had given permission for the photos to be done.

"The brief was to get some photos in and around Parliament and to make sure the Beehive was in the back-ground. We certainly wouldn't want the (protest) banner in the back-ground."

The photos on Parliament steps would now be canned and other notable landmarks around the precinct would be used instead.