Stuart Nash has apologised to the prime minister, cabinet colleagues, his staff and the "amazing hard working Labour members of Napier" for letting them down and causing an "unwanted distraction".
He also apologised to his Napier constituents and said "for now, I will continue to be your local MP and will work hard to make sure you get everything you need and deserve in your journey of recovery after Cyclone Gabrielle".
"Most of all, I offer an apology to my family. These events after often more traumatic for our partners and children than they are for us; so, to Sarah and our wonderful children, I am truly sorry. You have supported me in good times and bad, and for this I am eternally grateful.
Nash said politics was about delivery and getting things done, but he could tend to "go hard when often a softer approach would perhaps deliver superior results over the longer term".
He "played outside the rules and that's unacceptable".
"I do want to be clear. I got this wrong. Too many times. Fair cop. The Prime Minister did what he needed to do. I accept this with humility."
While he lost his job as a minister, Nash remains the Labour Party MP for Napier, and said "for now" he would continue in that role to help the electorate through the recovery after Cyclone Gabrielle.
There would not be an "unnecessary, messy and expensive by-election... the last thing this city needs", he said.
Nash said it was now time to take his wife's "sage advice" that he needed to "work on my EQ".
"So now it's on to the next challenge. There will be no unnecessary, messy and expensive by-election - this is the last thing our city needs.
"So, for the meantime I will remain as the MP for Napier and continue to advocate for solutions to the issues that are important to the people of my hometown; first and foremost, recovery from Gabrielle."