Ngāi Tahu has strongly criticised David Seymour and New Zealand's ACT party over the Treaty Principles Bill, which aims to "redefine" Te Tiriti o Waitangi (the Treaty of Waitangi).

Ngāi Tahu is the principal Māori iwi (tribe) of Aotearoa's South Island.

The southern iwi described the ACT leader as "naïve", "politically clumsy," and "misleading", as reported by Te Ao News.

"David Seymour and ACT are misconstruing history," Te Rūnanga o Ngāi Tahu kaiwhakahaere (chair) Justin Tipa said on Friday.

"You can't have a reasonable debate with a person or party who distorts the truth.

"ACT's true purpose is a direct attack on tino rangatiratanga (self-determination), guaranteed to iwi and hapū (sub-tribes) in Article II of the Treaty."

In a news item on the iwi's website, Mr Tipa emphasised ACT's attempts to diminish rangatiratanga under the bill.

He said Māori people are angered by the Coalition Government's Treaty Principles Bill because it undermines their right to self-determination.

He highlighted ACT's earlier attempt to reduce rangatiratanga by suggesting it applied only to individual property rights.

ACT claims iwi and hapū can only exercise rangatiratanga with state approval, which Mr Tipa said contradicts ACT's small government stance.

Mr Tipa said Ngāi Tahu is focused on empowering its people and isn't interested in the conversation ACT is leading.

"ACT's claim that it wants to create certainty in law is false," Mr Tipa said.

"David Seymour's announcement last week was a blunder, with even his officials warning that the Bill adds more uncertainty to our constitutional framework."

He argued that the Treaty Principles Bill proves ACT isn't capable of leading discussions about New Zealand's future, describing Mr Seymour's efforts as politically inept and unhelpful.

Mr Tipa called for discussions on empowering communities rather than divisive rhetoric.

Ngāi Tahu wants to focus on exercising rangatiratanga for the benefit of Māori and all New Zealanders, addressing issues like housing and infrastructure, while empowering local communities.

He criticised the Parliament who will now spend nine months debating the bill, which Prime Minister Christopher Luxon has already said will be scrapped next year.

Mr Tipa said Prime Minister Luxon and Deputy Prime Minister Winston Peters had let the situation escalate, arguing unilaterally redefining the Treaty's principles would damage the basis of Treaty Settlements.

Ngāi Tahu aims to unify the country by hosting 'Te Pūnuiotoka', a hui ā motu (national gathering) in October for iwi and hapū leaders to discuss how rangatiratanga can improve regional development and national prosperity.

In contrast, Mr Seymour reiterated the Treaty Principles Bill is meant to provide clarity and promote national discussion about the Treaty's place in New Zealand's constitutional system.

He argued the Treaty ensures equal rights for all New Zealanders and criticised interpretations of tino rangatiratanga that offer different political rights based on ancestry.