Faafoi said he assumed that Kerrison was now upset with him, but had not spoken to him recently because it would not be appropriate. He apologised to him for giving the impression he would support him but not following through.
Ardern said she had confidence in her minister and that his dealings with Kerrison did not constitute a conflict of interest.
"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," Faafoi said in a statement this afternoon.
"I know I need to be more upfront in the future about what I can and can't do if I'm approached for help.
"I was contacted by Jason, who is 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.
READ MORE:
• 'Bro I have a plan': Kris Faafoi offered to help in friend's immigration case
• Premium - Political Roundup: Should Kris Faafoi be sacked?
• 'Celebrities get influence': Bridges slams Labour over Faafoi case
• Premium - Audrey Young: Kris Faafoi is in trouble but just how much?
"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 I told Mr Kerrison he needed to talk to his local electorate MP and I called Matt King to let him know about the case.
"I contacted Jason's mother to offer to write a supporting letter, as I had been advised I could, and got some more details for the letter. However, I never wrote the letter.
"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.
"In hindsight I 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.
"I acknowledge this is messy and you could read other meaning into my messages. But I can hand on heart say I wasn't doing anything to advance the case, and the messages just reflect me not wanting to let a mate down. In hindsight I should have been clearer with him.
"I've apologised to the Prime Minister and understand I have let her down. I know I need to be more upfront in the future about what I can and can't do if I'm approached for help."
Ardern said Faafoi should have dealt with the issue in "a much clearer manner".
"I've made my views on that very clear to him."
She said Faafoi was not Associate Minister of Immigration at the time, and he had no ministerial responsibilities for immigration matters.
"Once Kris decided to direct Jason Kerrison's request to another MP to progress, Kris should have brought the communications to an end and told Mr Kerrison directly he couldn't help any further.
"While Kris' communication didn't have the clarity I expect, the Minister has assured me he never actually took any actions that sought to influence the case.
"Given that, this is not a case where the Minister has failed to manage a conflict of interest appropriately. But as the Minister has acknowledged, his texts created an unhelpful impression that there was some influence he could bring to achieve a favourable outcome.
"While it may be more comfortable for Ministers to give the impression they are helping, I would rather they were upfront and tell people if they can't assist and give them the reasons why, and point them to someone who can help.
"I've told Minister Faafoi I expect better from him."
It was revealed yesterday that Faafoi offered to assist his friend and Opshop singer Jason Kerrison's family in getting a visa.
Messages between Faafoi and Kerrison published by Newshub showed that he said he would talk to "people who can speed things up".
In October, Kerrison said he was "gutted" to hear Immigration New Zealand's decision to reject his stepfather's application for residency.
His mother, Jude Kerrison, married Gitonga "Mich" Obadiah, a Kenyan national, in 2017.
But Obadiah's residency was rejected, as Immigration New Zealand questioned the legitimacy of their relationship.
Facebook correspondence showed that agreed to help Kerrison, and at one point asked for Kerrison's stepfather's surname and immigration number.
"Bro I have a plan - but it can't be plastered over [Facebook],' Faafoi wrote to Kerrison.
Immigration New Zealand said this afternoon that it had no record of representation or involvement by any minister or MP in relation to Obadiah's case.
It also confirmed that Kerrison's stepfather was declined a partnership visa in August because he did not meet immigration requirements.
"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," said Nicola Hogg, general manager border and visa operations.
"The onus is on the applicant to provide sufficient evidence to demonstrate they meet immigration instructions."
