Labour leader Phil Goff has labelled Chris Carter a "narcissist" and says the public thinks the ousted MP is "a jerk".
The expulsion of Mr Carter from the party on Monday and the resulting fallout have been the main headline for Labour as it prepared for its annual conference starting today in Auckland.
Mr Goff told the Herald he did not believe the fuss had damaged the party.
"The Chris Carter affair is doing the Labour Party no great harm out there among the people I'm talking to. They think he's a jerk."
While there would be Labour members at the annual conference who were close to Mr Carter, he believed they knew the MP was responsible for his own downfall.
"What has damaged Chris is the huge sense of entitlement and an approach that has been totally self-centred and narcissistic."
Mr Goff said he had never been asked why he was being "mean" to Mr Carter.
"I have been congratulated by people for getting rid of him."
He believed Mr Carter would "disappear into history".
The rare personal criticism of Mr Carter shows Mr Goff's patience with him has run out afterthe MP's threats to spill caucus secrets or name people he claimed were plotting against the Labour leader.
Mr Goff said he had not asked any of his MPs if they had met Mr Carter to discuss his leadership, as the rebel has claimed.
"No, because I'm not paranoid. I just think it's nonsense. I'm not the least bit paranoid, that's not one of my failings."
Mr Goff said he kept in close contact with his caucus.
"Give me the credit to know my caucus well enough to know what's going on. I put myself forward for leader because I thought I was the best person, I will continue to do that while I think I'm the best person for the job."
Told of Mr Goff's comments to the Herald, Mr Carter said he was not narcissistic, although "you're never the best judge of yourself".
"But I would have thought that narcissistic people are unusually - excuse the Westie expression - up themselves. One of the things all of my staff, and anyone who has any dealing with me around Parliament have probably all found that while I might have a temper, I've certainly never been up myself.
"So I'm now a jerk, a liar, narcissistic, disloyal, dishonest and treacherous. Isn't that rather an overreaction from Mr Goff?"
Yesterday on Radio Live, Mr Carter also mentioned Shane Jones as one of those he believed could be a better leader than Mr Goff. He has previously refused to name them.
Mr Jones expressed disbelief, saying, "I fear that Chris Carter's illness is worse than we expected."