National Party leader John Key says he could not stop New Zealand First abstaining and allowing a National led government to be formed, but he would not negotiate with the party.
National has ruled out working with New Zealand First, although its leader Winston Peters says he will work with anyone after the election.
But Mr Key says National will not do a deal or make policy concessions to New Zealand First, even if it abstains on confidence votes.
"I can't stop a political party abstaining and there are aspects of policy where New Zealand First and National agree with one another. We for instance have retained the floor of superannuation at 66%, something Mr Peters advocated for. But we're not intending to go into negotiations or discussions with New Zealand First."
Mr Key says if Mr Peters holds the balance of power, he will take the "baubles of office" and install a Labour government.