A war of words over ACT's plans to re-define the principles of the Treaty.

Prime Minister Chris Luxon has said National would support the Bill to the select committee stage.

But ACT Party Leader David Seymour says National hasn't ruled out supporting it further.

"We've got no commitment any further either way, and I suspect that first of all- this is a debate we need to have, and I suspect they'll recognise that. Second of all, it's a lot more popular than people are giving it credit for."

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