The head of the Labour Party's Māori caucus says many of those protesting the construction of 480 new homes in at Ihumātao don't understand what the local iwi has achieved.

Hundreds of protesters have descended on the land, in Auckland's Mangere, demanding it be given back to Māori. A small number have been arrested, and the crowd is expected to swell on Friday with the arrival of four Green Party MPs.

"Colonisation is actually continuing with this land confiscation," Greens co-leader Marama Davidson told Newshub.

The land is owned by Fletcher Building. In 2014 32 hectares of it was designated a Special Housing Area.

In a move RNZ described as "unusual", the company struck a deal with Te Kawerau a Maki, the local iwi. This saw eight hectares handed back, the housing project scaled back, views of the maunga protected and some of the homes placed into a shared equity scheme with the iwi, which described the deal as "better than anything we have ever achieved from Housing New Zealand or the Crown".

Labour's Willie Jackson said the mana whenua saw an opportunity and took it.

"They'd been shut out altogether, all of a sudden they had an opportunity in terms of housing. And they're being condemned for that."

Te Kawerau a Maki originally tried to stop the family which owned the land from selling it to Fletcher, "but had no legal recourse to stop the transaction", said chairman Te Warena Taua.

"We decided the next best thing was to negotiate with Fletcher to win significant rights and concessions for our people."

Taua said some of the protesters have been using the situation to "rewrite history for their own purposes" by claiming it was a burial site, which he says isn't true.

"They do not have the authority to speak for our people and sadly they are misguided in their assertions."

Jackson said he empathises with the protesters, saying the outcome is "an injustice upon an injustice upon an injustice", but having bought into the settlement process, the iwi has done the right thing.

"The people who made the deal are being rubbished - it's like, 'silly old kaumatuas, sellouts' and all that. Whatever. They took an opportunity because this is the process that our people have bought into...

"[The protesters] understand it's been an injustice from the start and they want to go down this way of getting all the land back. I understand that."