Two brothers who assaulted the Prime Minister at Waitangi last year are occupying a privately owned former motor camp to stop the land being developed.

John and Wikatana Popata have taken down real estate agents' signs at the Taipa property in the Far North and have been staying on the land since the weekend.

Their protest has the backing of the local Ngati Kahu iwi.

In an email, the two men - who were convicted in June after grabbing and jostling John Key as he arrived at Te Tii Marae at Waitangi - outlined two demands: "No land to be sold at Mahaetai [Taipa], so you property investors or house buyers don't buy land here, and we want our land returned to Ngati Kahu for nothing."

Yesterday, John Popata said it was time for the "stolen" land to be returned.

If that didn't happen, success might be measured in buyers keeping away.

"In our hearts we want it back. But would you buy land here if Maori were jumping up and down about stolen land?"

Ngati Kahu has not settled its Treaty claims. Chief negotiator Margaret Mutu said the tribe was edging towards a settlement but many in the iwi were upset that private land, which is not covered by settlements, would not be returned to them.

She said Ngati Kahu supported the stand the occupiers were taking because it reflected real concerns.

"By current standards, our deal is one of the best in the country ... but we still only get back about 20 per cent of our land," said Dr Mutu, who is also professor of Maori studies at Auckland University.

"Taipa is the centre of Ngati Kahu. It's an iconic place as far as we're concerned because it's where so much of our history is."

Development had boomed along the coast in the past decade and Maori found it hard to watch, Professor Mutu said. "They watch the rich Pakeha build and they don't like it."

Tai Tokerau MP Hone Harawira, who supported the Popata brothers after the incident with Mr Key, said the fact they had assaulted the PM did not affect their credibility within the tribe.

The LJ Hooker agency in Mangonui is one of several real estate businesses trying to sell the land. Sales manger Michael Ponsonby yesterday declined to comment.