The Labour Party has refused to renew the party membership of Auckland mayoral candidate and former Cabinet minister John Tamihere.
Tamihere said he is considering a legal challenge to the decision because he had been given no just cause for it.
He sent in his application from the Labour Party website in December with a $100 donation.
It was returned to him this week after a decision by the party's ruling New Zealand Council at the weekend to reject his membership.
"I haven't been a member of any other political movement in my life."
Labour Party president Nigel Haworth declined to make any comment, saying a process was in train.
"The party is still addressing the issue and until everything is finalised in the process of addressing it I can't comment."
Tamihere said he was sure it was about the fact that Labour's ruling New Zealand Council had endorsed mayoral incumbent Phil Goff, a former Labour Party leader, at a meeting last December when speculation about Tamihere's candidacy emerged.
Goff has yet to declare that he will be seeking a second term but he ran as an independent candidate last time.
"I'm just amazed that a group of people not from Auckland can determine who the mayor should be in that ruling council," Tamihere said.
He was not told why his membership bid had been rejected.
"There is a clause that allows them to review membership because Jack the Ripper could get on or whoever. They are spuriously using that clause to deny me membership."
He said he was considering a judicial review of the rejection "because I don't like injustice."
"I'm 100 per cent certain this is about the Auckland mayoralty," Tamihere said.
Tamihere said he had been a member of the Labour Party since he was aged 8, when his father signed him up. He had last renewed his membership in 2017 and it had lapsed some time in 2018.
Rudy Taylor, one of the representative of the party's Māori council, Te Kaunihera Māori, on the New Zealand Council, did not believe Tamihere had received natural justice.
He would not disclose the discussions that had taken place before the council voted to reject his application to renew his membership.
"I am disappointed that people saw JT in a different light…they could have had more heart to the thinking about JT but it was a democratic vote and they have their choice."
Taylor said he had also held a Te Tai Tokerau electorate meeting at Waitangi on February 6 with Haworth to discuss the New Zealand Council's decision to endorse Goff.
The clear message had been that the Māori council preferred to make their own decisions on whom to support for the Auckland mayoralty, Goff or Tamihere.
He said natural justice would have meant both Goff and Tamihere got to appear before the council before it had made a decision to endorse Goff.
Tamihere, aged 60, is never far from controversy. He was an MP from 1999 to 2005 and a Cabinet minister from 2002 to 2004. He stepped down as a minister pending an inquiry around tax payments on a golden handshake he received after leaving the Waipareira Trust.
He resigned but was later cleared. However, he fell out with many colleagues in 2005 when Investigate magazine published an article based on trenchant criticisms of them during what he thought was a confidential discussion.
He also lost his job as talkback host for taking a skeptical view during the height of the Roast Busters revelations, when teenage boys bragged about having sex with drunken young girls.
He is an occasional columnist for the New Zealand Herald.