Waikato-Tainui leader Tukoroirangi Morgan dismisses David Seymour as "a political idiot" in the latest episode of 30 with Guyon Espiner.
Morgan, a former broadcaster and politician, describes the ACT Party leader's Treaty Principles Bill as "a nonsense".
The bill proposes revisions to the interpretations of the three treaty articles, which would - amongst other changes - limit Māori co-governance arrangements included in Waitangi Tribunal settlements.
"You've got a political idiot here, who is trying to modernise a document that will make the 1840 signing a nullity," Morgan says.
"It's an attack on an agreement that was enshrined in a trusting way by those Rangatira in 1840."
Prime Minister Christopher Luxon has said the government is not planning to support the Treaty Principles Bill beyond the select committee stage but will not rule it out completely.
If the bill did go beyond a first reading, Morgan says the resulting protest action would be at a level "never seen in the history of this country before".
"There are those of us who ... will not sit still and remain idle," he says.
"If this bill is passed, and it goes beyond the first reading, there'll be hell to play, simple as that."
Morgan, who was one of the founding members of New Zealand First and president of Te Pati Māori from 2016-2017, told Guyon Espiner he wasn't interested in returning to central politics, but as chairperson of Waikato-Tainui still had "lots" of political shots to fire.
"We're an iwi now who has economic power, nearly $2.4 billion of assets.
"We're capable of doing what we need to do to protect that which is our own and protect the future of our young ones. Because in the end, it's the young ones who we serve."
The interview with Morgan was recorded earlier this year and is released today as episode eight of 30 with Guyon Espiner.
In episode 3, Seymour criticised policy-makers "lazily categorising people by race". He has said the Treaty Principles Bill will give all New Zealanders "the same respect and dignity, including equality before the law."
* 30 with Guyon Espiner comes out every week on RNZ, Youtube, TVNZ+ and wherever you get your podcasts.
Tukoroirangi Morgan Photo: RNZ / Cole Eastham-Farrelly
'An opportunity that beckons our people'
Morgan says the election last year revealed "an emergence of young Māori who are much more articulate, much more visionary about where they want to go".
"But unless our people get serious about politics, and make the jump, and go back onto the Māori roll, we will always be spectators to the political process."
The Māori roll was established in 1867 to ensure that Māori could participate in the electoral process.
At that time, the right to vote was linked to land ownership under individual title, which was all but non-existent in te ao Māori.
There are seven Māori electorates, with each guaranteeing a seat in Parliament.
New Zealand citizens of Māori descent can choose to enroll on either the general electorate roll or the Māori electorate roll.
"There is an opportunity that beckons our people - to go from the Pākehā roll back onto the Māori roll," Morgan says.
Māori electorates and general electorates are separate, each electing their own member of parliament.
According to the electoral commission there are 291,825 voters currently registered on the Māori roll.
"We will always be bystanders and a supporting act to the main party, unless we jump back onto the Māori roll, and as a result create more Māori seats."
Since the introduction of MMP, ethnic diversity in parliament has improved, with Māori representation now at nearly 27 percent.
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