Māori Party co-leader John Tamihere says National is "pushing Māori away" but says the party could still go with either them or Labour if re-elected at September's election.
National's been under fire for not having any Māori MPs in its top 12, in the new line-up revealed on Monday.
The issue blew up further when, in defending the caucus' diversity, newly-selected deputy leader Nikki Kaye incorrectly said MP Paul Goldsmith was Māori.
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The racial tensions intensified on Wednesday after National MP Judith Collins said she was "sick of being demonised" for her ethnicity, reacting to questions being asked by Labour MP Tamati Coffey about the treaty partnership during a select committee meeting.
New leader Todd Muller has also drawn criticism from Māori in his Bay of Plenty electorate after launching a petition to overturn an Environment Court decision ordering the Bay of Plenty Regional Council to establish marine reserves on reefs around Motiti Island about 10 km off Tauranga Harbour.
Local hapū had been advocating for such protections for decades.
Tamihere said the latest actions showed National was desperate and was reverting to its "true colours".
"Jacinda Ardern has led the country through major events, from the mosque attacks, Whakaari and now Covid-19. They've really solidified their support.
"National is failing to battle against that, and so is heading back its base instinct, to its main white vote, and is pushing Māori away."
This made it harder for the Māori Party to consider working with them if re-elected, but Tamihere said they were not ruling it out.
"On Motiti it is quite clear [Muller] is in opposition to Māori interests, and the more he opposes such rights and justice issues for Māori the worse it gets for us doing business with them.
"But we are not going to pre-empt that decision on who to work with, it is what we agreed to at our leadership conference over the weekend.
"We will only make a decision after the election when the cards are dealt, then we will go back to our constituency.
"We don't determine who has the majority to make up the next government, that is mainstream voters, so it would be silly to predetermine the election."
Having been in Cabinet positions before, Tamihere said either way Māori interests would still always be weighed against the majority.
"That is why I am in the Māori Party.
"Both major parties are driven by mainstream Pākehā and led by them."
While there were no Māori MPs in National's front bench, Tamihere said that was better than "tokenism".
"Muller cleaned house and in doing so knocked off two Māori leaders in Bridges and Bennett, so that is a clear indication to us."
If the possibility of working with National did arise, they would be pushing for a stronger role than under the John Key-led government, where Māori Party MPs were given ministerial roles but kept outside of Cabinet.
"What Key did was absorb Māori problems and then delegate them to us. We would not accept that, and would be pushing to be inside Cabinet."
National Party leader Todd Muller's office has been approached for comment.