New Zealand First leader Winston Peters is defending the swift expulsion of MP Brendan Horan from the party caucus.
Mr Horan continues to deny allegations relating to his late mother's finances, including that he stole from her or misappropriated any of her money or assets.
Mr Peters says he has been presented with evidence he describes as "irrefutable and irrebuttable" over the past week.
On Tuesday, he told Parliament that he had received information that led to him lose all confidence in the list MP. The caucus went on to swiftly expel Mr Horan and Mr Peters called on him to quit as an MP altogether.
Some political parties say Winston Peters has acted too quickly against Mr Horan. But Mr Peters told Radio New Zealand's Checkpoint programme on Wednesday that he does not regret his decision.
"I'm content and confident that I've done the right thing. I did not make a rash decision on this - I gave it some very, very serious consideration. But when I had the evidence that would be irrefutable, irrebuttable, I acted."
Mr Peters said he came to the conclusion Mr Horan could no longer be a New Zealand First MP four or five days earlier, but waited to get as much information as possible and to make sure he was acting properly.
He says the information he has received will become public in a forum other than Parliament, but can't say when that will happen.
Brendan Horan returned to Parliament on Wednesday where he will be allocated a new office as he takes up the role of an independent MP. He then went on personal leave and is expected back next week.
Mr Horan told media he was surprised by Mr Peter's statement to the House, but does not intend to fight the expulsion from the New Zealand First caucus.
"If the leader of the party doesn't want you, then I'm not one to try to go begging back. But my core values haven't changed. My beliefs haven't changed."
In the past there have been list MPs, who have either been expelled from or quit their caucus, and served out the term as an independent.
As an independent, Mr Horan will cast his own vote - unless he is absent from the House - in which case he may choose to have another party cast it on his behalf.
Prime Minister John Key says it's too soon to say whether the Government would cast a proxy vote.
Parties say Peters has jumped the gun
The Green and Maori parties on Wednesday accused Winston Peters of being too quick to sack Brendan Horan from his caucus.
Greens co-leader Russel Norman says Mr Peters has not followed natural justice in his sacking of Mr Horan. Maori Party co-leader Tariana Turia agrees, saying people are innocent until proven guilty.
In 2004, Mrs Turia quit the Labour Party and served as an independent before establishing the Maori Party. She believes Mr Peters has acted prematurely and should have waited for a more formal inquiry.
Mrs Turia has offered her support to Mr Horan, saying she knows what it is like to be in what is a very lonely position.
MP denies wrongdoing
After making his statement to Parliament, Winston Peters declined to discuss details of material he received on allegations against Brendan Horan, to avoid any legal action.
"I'm not going to be subject to people spraying defamation writs that cost you a fortune, no matter how correct you might be or not, and that is used to actually muzzle people. I did not wish to expose myself to that."
Mr Horan released a statement through his lawyer Paul Mabey denying any wrongdoing in response to allegations relating to his late mother's finances.
Mr Mabey said none of the allegations had ever been put directly before the MP, who is confident he would be cleared of any wrongdoing if an independent inquiry was held.
Mr Horan has made it clear he intends to stay on in Parliament, but Labour Party deputy leader Grant Robertson says most New Zealanders believe that if a list MP leaves their party caucus they should leave the House.
Mr Robertson told Radio New Zealand's Morning Report programme on Wednesday that with the recent review of MMP, it is a good time to look at the issues of of credibility when a list MP is no longer in the party caucus.
Green Party co-leader Metiria Turei does not think party leaders should have the power to expel MPs from Parliament, as she says that could lead to a politically motivated decision with no process to ensure justice.
United Future leader Peter Dunne said a list MP is elected on the basis of voters' support for a party.
Mr Dunne says as long as Mr Horan is member of the New Zealand First Party he could stay on as MP - but if his membership is terminated, he should go.
Mr Dunne left the Labour Party in 1994; he says it was pretty traumatic and something he would not do again.