Former Labour MP Chris Carter says his expulsion from the party last night was an overreaction and the party leadership has been "petty".
The Te Atatu MP was expelled during a seven-hour meeting of the party's national council yesterday.
The council found he had breached rules by acting in a misleading manner likely to cause internal discontent and encourage external ridicule.
While Mr Carter last week accepted he would not stand again in his Te Atatu seat he hoped to remain a party member. He has already been thrown out of the party's parliamentary wing after sending an anonymous letter to the media in July, which said a coup was planned against leader Phil Goff because he couldn't win the next election. He was quickly outed as the letter's author.
At the time Mr Carter was smarting from criticism of excessive spending on travel while he was a minister and in opposition.
Mr Carter told Radio New Zealand he heard about his expulsion on the radio this morning.
"I just think it's a ridiculous over reaction to make Phil Goff look strong."
The council did not listen to his defence and he felt as though he was appearing before the inquisition, Mr Carter said.
He said he would decide next week whether to appeal the decision.
"I did a stupid thing, it was born out of anger, it didn't happen for no reason -- I felt as though I'd been used as a scapegoat by Phil Goff over this whole travel business."
Mr Carter said the party had been unprofessional and petty in its handling of the situation.
"Nothing I put in my letter was incorrect, the way I did it was ridiculous, stupid."
He said he would not do it again.
Mr Carter said he would talk to family and friends about his future but planned to serve the rest of his term as MP for Te Atatu.
Party president Andrew Little said Mr Carter's arguments were considered and the 17 members in the meeting -- six by teleconference -- did not have a predetermined position.
"When it came down to it, the council considered that the actions that he took were very serious, had the author of his letter to the gallery not been revealed or disclosed it would have caused considerable harm to that caucus and the way it operates and there's no question that the publicity that the whole enterprise generated in the days following caused damage to the party," Mr Little said.
The meeting started at 5.30pm and ended just before midnight, Mr Carter left about 9.30pm through a back door to avoid media.