Judith Tizard, has accused former Labour Party president Andrew Little of bullying her, over her possible return to Parliament.
Mr Little, who stepped down as Labour's president on Saturday, publicly stated the party would prefer it if Ms Tizard, and four other former MPs at the top of Labour's list, did not replace Darren Hughes, who is to resign on Tuesday over a police investigation.
That would allow Labour's Manurewa candidate, Louisa Wall, to take his seat.
Judith Tizard announced on Sunday that she will not return to Parliament.
She said it was a hard decision to make, as she hates bullying.
"When you shout at somebody in the news media rather than talk to them face to face, or even over the telephone, I consider it bad manners. It could be interpreted as nothing else but bullying," she said.
Ms Tizard said Labour leader Phil Goff should analyse whether he can win the election, and if he can't, he should stand aside.
Louisa Wall says Ms Tizard made the right decision given she is not going to stand in the next election which is just a short time away.
Ms Wall says she expects a decision to be made within the next week on who will fill the seat.
Mr Goff says he has spoken to all the possible candidates and the others have indicated they have moved on in their lives.
New party president Moira Coatsworth has also indicated that Ms Wall is the party's preference.
Ms Wall, 39, is Labour's candidate for Manurewa and is number 43 on the party list. She previously served in Parliament for eight months in 2008 when Ann Hartley resigned, but then did not win back her seat at the last election.
Ms Tizard, 55, was an MP for 18 years until she was defeated in Auckland Central in 2008. She was the assisting minister for Auckland issues for a time.
Mark Burton, the next candidate on the Labour list, has also confirmed he would not take Mr Hughes' place.
