The Green Party has rejected Kennedy Graham's request to be admitted back into the party fold and be on the party list for next month's general election.
Dr Graham and David Clendon earlier this week resigned at short notice from the party's 14-member caucus over co-leader Metiria Turei's admission she committed benefit fraud during the 1990s.
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Ms Turei later quit as co-leader, which potentially opened the way for Dr Graham to return.
In a statement on Saturday morning, the party said it had declined his request to be a list candidate for next month's election.
"The executive concluded that he had breached the party's Candidate Code of Conduct in a serious manner, and therefore decided to exclude Mr Graham from the party's pool," party co-convenor Debs Martin said.
"We thank Kennedy for his many years of service, and the executive finds it regrettable that events have led to this outcome."
Mr Clendon has said he did not want to return to the party's caucus.