A bill that proposes making Monday a public holiday when either Waitangi Day or Anzac Day fall on a weekend may not need the support of the Government.
The legislation, in the name of Labour Party MP David Clark, is due to be debated in about six weeks.
Prime Minister John Key says National Party MPs have asked the Labour Department for more advice on the proposed changes.
Mr Key says there are concerns about the economic cost of any change, and whether it would devalue both days.
He says a decision on how his party will vote will be made at its next caucus meeting in a fortnight.
But even without National's support the bill could still become law if other parties vote for it.
The only party to openly oppose it at this stage is ACT.
The Government's support partner, United Future leader Peter Dunne, says he would support the bill.
He says it is only fair New Zealanders receive the Monday off if Waitangi Day or Anzac Day fall on a weekend.
The Maori Party hasn't considered it yet, but co-leader Pita Sharples is relaxed as long as celebrations still continue on Waitangi Day.