Last night Mr Carter took a swipe at the "nasty and unfair" media stories, and thanked his partner of 38 years Peter Kaiser for sticking by him, despite "media intrusion into our personal lives".
Mr Carter was the first openly gay MP.
"I knew that gay and lesbian teenagers faced huge amounts of prejudice and had few affirming messages or positive role models," he said.
Together with gay MP Tim Barnett and transsexual MP Georgina Beyer, "we broke a glass ceiling".
He was most proud of his electorate work. "I can truthfully say that there is not a house in my electorate, or a letter box or probably even a dog that I don't know personally."
Mr Carter entered Parliament in 1993, but lost the Te Atatu seat in 1996 before regaining it in 1999.
He held several ministerial portfolios, including conservation, ethnic affairs, local government, housing, building issues and education.
"It is time for a change for me but I will always consider that it was an honour and a privilege to have served as a West Auckland representative in this Parliament for 15 years."
Mr Goff said he wished Mr Carter well in his new career.