Kris Faafoi has been given a "stern talking to" by Prime Minister Jacinda Ardern over his handling of an immigration case involving his family friend, Opshop singer Jason Kerrison.
Faafoi, a Cabinet minister, said in a statement on Friday he needs to be "more upfront in the future about what I can and can't do if I'm approached for help".
"I have apologised to the Prime Minister and understand I have let her down in regards to my dealings with Jason Kerrison over an immigration matter concerning his family."
The Prime Minister said Faafoi was not Associate Minister of Immigration at this time, and he had no ministerial responsibilities for immigration matters.
But she said she has spoken to him about his "poor handling of the issue".
"I have confidence in Kris as a hardworking and effective minister, but this should have been dealt with in a much clearer manner, and I've made my views on that very clear to him."
Ardern said while it may be more comfortable for ministers to give the impression they are helping, she would rather they were upfront, refuse, and provide the reasons why.
"I've told Minster Faafoi I expect better from him."
Newshub revealed on Thursday a series of text and Facebook messages between Faafoi and Kerrison, in which Kerrison asks Faafoi for help with his step-father's declined partnership visa application.
Faafoi tells him he'll "talk to the people that can speed things up" but "can't put anything in writing", and soon cuts off communication.
Faafoi told Newshub he'd stopped replying to Kerrison's messages "because it wouldn't be appropriate", but the National Party says by then he'd already gone too far.
"If what's alleged is proven correct, I think Kris Faafoi's position is untenable," National leader Simon Bridges told Newshub on Friday.
Faafoid said in his statement on Friday that he has apologised to the Prime Minister and "understand I have let her down".
Faafoi acknowledged in the statement that he was contacted by Kerrison, "an old family friend, to see if I could help him with his step-father's immigration case".
"Rather than telling Jason straight away I couldn't do anything to help him, I said I would look into it; as MPs are allowed to do in these cases," Faafoi said.
"I made contact with the Associate Immigration Minister's Office to seek advice on the appropriate process. They told me to refer him to his local MP and that I could write a support letter."
Following that conversation, Faafoi said he told Kerrison he needed to talk to his local electorate MP, National's Matt King, and Faafoi said he called King to let him know about the case.
A National Party spokesperson has confirmed Faafoi contacted King on October 11.
The spokesperson confirmed Faafoi said Kerrison's mother needed help on an immigration matter, and asked if King could assist.
"King told Mr Faafoi that Jason Kerrison should contact his office. His office was never contacted," the National Party spokesperson said.
Faafoi said he contacted Kerrison's mother to offer to write a supporting letter, "as I had been advised I could", and got some more details for the letter.
"I never wrote the letter," he said. "I stupidly created an impression through my messages that I was following up on it when in fact I wasn't.
"I was uncomfortable with him messaging me pretty regularly on it and you can see I stopped responding to his texts."
Faafoi said in hindsight, he should have "just been clear and told him I couldn't help and just to deal with his local MP".
"But aside from checking to see what the proper process was for me to follow I took no other actions, and specifically took no actions to advance it, influence it, or advocate for it."
Immigration New Zealand (INZ) confirmed to Newshub that Kerrison's step-father, Gitonga Micheu Obadia, was declined a partnership visa on 2 August 2019 "as he did not meet immigration requirements as set out in partnership policy".
"To grant a visa under partnership policy, an immigration officer must be satisfied the applicant is living with their partner in a genuine and stable partnership," Nicola Hogg, INZ border and visa operations general manager, said.
"The onus is on the applicant to provide sufficient evidence to demonstrate they meet immigration instructions.
"INZ has no record of any representations or involvement by any Minster or Member of Parliament in relation to Mr Obadiah's case."
Faafoi was promoted to Cabinet minister in the Prime Minister's Cabinet reshuffle in June.
He took on the role of Associate Housing Minister, in charge of public housing and tackling homelessness.