The Maori Party says National's opposition to swearing an oath to the Treaty of Waitangi was a "disturbing" move which recalled former leader Don Brash's stance on treaty issues.
Parliament was expected to debate a Maori Party bill today which would allow people to uphold the treaty when making a statutory oath.
The legislation had the support of Maori, Greens, Mana and Labour at the first reading, but was unlikely to pass because National, Act and New Zealand First opposed it.
Maori Party co-leader Pita Sharples said National had entered into a relationship with his party to show how people with different kaupapa [principles] could work together constructively.
He accused National, a coalition partner, of contradicting itself on the treaty.
"The Prime Minister says National acknowledges the status of tangata whenua and recognises the treaty as the founding document of this nation, but his caucus deems it 'not necessary' to allow any MP to pledge to uphold the treaty in their work on behalf of all New Zealanders."
At present, New Zealanders swear an oath of allegiance to the Queen. Maori, Green and Mana MPs have previously attempted to include the treaty when swearing in as MPs but have been told to start again by the Speaker.
The Maori Party felt the bill, sponsored by MP Te Ururoa Flavell, was a small but symbolic step towards recognising the treaty.
Dr Sharples said National had made good progress on settling historic treaty claims. But the party appeared to be shifting its position due to pressure from a small minority which promoted discontent over the treaty and Maori issues.
"Their opposition to my Private Member's Bill is a disturbing move, which we might have expected from former leader Don Brash, or former Act MP Muriel Newman and her Centre for Political Claptrap which wants to 'abolish the Treaty'."
Act Party leader John Banks said his party regarded the Treaty of Waitangi as a significant constitutional document.
But he emphasized that New Zealand was a constitutional monarchy and oaths of allegiance should be to a person and not to constitutional documents.
"Therefore, Act will not be supporting Mr Flavell's bill to allow people to swear an Oath of Allegiance to a constitutional document."
Labour said it held some reservations about the law change but would support it to select committee.
Swearing an oath to the Treaty of Waitangi
For: Labour (at first reading), Greens, Maori, Mana
Against: National, New Zealand First, Act
Undecided: United Future