The discovery of human ashes deposited at the base of New Zealand's largest kauri tree - Tane Mahuta - has horrified local iwi Te Roroa, who may consider a rahui if the desecration continues.

The iwi says bereaved families often scatter ashes at the foot of Tane Mahuta and other giant trees in the Waipoua Forest.

At a recent hui, Te Roroa elders expressed concerns the forest was becoming a dumping ground for cremated human remains.

Kaumatua Garry Hooker said he doubted bereaved families meant to cause offence by dumping the ashes under the giant tree, but the practice was objectionable to iwi.

He said the concept of human remains being mixed in an environment where cultural food harvesting of aruhe, nikau, kumarahou, watercress and other plants takes place was abhorrent to Maori, and demeaning to the deceased.

Mr Hooker said that in ancient Maori culture to have eaten part of a another human was to insult them - it symbolised superiority over the deceased.

Te Roroa is also worried the ashes could harm the forest trees - including Tane Mahuta, thought to be up to 2500 years old.

He said the ashes could transport organisms which could do harm to the trees, which were already struggling from the effects of kauri die-back disease and possums.

While it has not yet been discussed, Mr Hooker said it was possible a rahui - a form of tapu restricting access to an area - could be imposed around Tane Mahuta if the practice continued.

This would necessitate the erecting of sign warning people not to dispose human remains in the area.

"This would be a shame - the forest is supposed to be for people to enjoy, not for rules and regulations," he said.

Kauri Coast's Department of Conservation, community relations manager Karen Joyce-Paki said the department did not condone the practice of disposing of human remains in this manner.

"The forest is not a cemetery."

She said DoC had not been approached by anyone, but any approach made would be appropriately directed to Te Roroa.

"People don't think of the consequences - just of the emotional connection - a lovely place for their loved ones to rest," she said.

Public submissions closed on Monday for a proposal to create a kauri national park at Waipoua Forest.