Hone Harawira says his allegiance to the Treaty of Waitangi is more important than his loyalty to the Queen.
The leader of the Mana Party was to have been sworn in by the Speaker of the House on Thursday afternoon.
But Mr Harawira was ordered out of Parliament's Debating Chamber for rejecting the rules by making a speech as he was taking his oath.
His ejection was matched with a waiata from supporters in the public gallery, before they were silenced by the Speaker, Lockwood Smith.
The MP for Te Tai Tokerau says he wanted to first affirm his allegiance to the Treaty of Waitangi, because it is more important to him than the oath to Parliament.
Outside Parliament, surrounded by about 100 party supporters, Mr Harawira assured people in the Northland electorate he still represents them, if not officially.
Mr Harawira says he will be back in two weeks' time when he says he will stick to the rules.
He resigned from Parliament in early May after leaving the Māori Party and won a by-election in June.