The Green Party's Sue Bradford has delivered an emotional valedictory speech to Parliament, saying her stand-out achievement has been removing from law the defence of using reasonable force against a child.
Ms Bradford told the House that is what she will be remembered for - whether she likes it or not - to the applause of MPs.
The Crimes (Substituted Section 59) Amendment Bill removed the defence of reasonable force when an adult was charged with assaulting a child. Ms Bradford's bill was was passed in May 2007, with only seven MPs voting against it.
"Removing the defence of reasonable force for the purpose of correction is the most significant thing that I have been able to accomplish here," she told the House on Wednesday.
An MP for 10 years, Ms Bradford says her decision to resign was prompted by her failed bid for the position of party co-leader, won by Metiria Turei.
Ms Bradford paid tribute to several politicians, including fellow Green MPs.
Former Labour Prime Minister Helen Clark was given a special mention, for backing the aspiring Green MP in the run-up to the 1999 election in the face of what Ms Bradford said were vicious attacks.
"I will never forget Helen Clark standing up publicly for me at that time in the media. Nor the Green Party for having the courage to support both Nandor (Tanczos) and I into high places on the party list, despite our backgrounds in radical and street politics, and lots of criminal convictions in my case."
She also thanked Miss Clark's successor, John Key, for sticking to his guns over National's support in amendments made to Section 59 of the Crimes Act regarding child discipline.
Ms Bradford will be replaced by the next person on the Green Party list, Dave Clendon, an Auckland-based small business adviser and former resource management lecturer.