Kenrick released the statement this evening after Williams was revealed to have read out an abusive message, apparently from a viewer, which turned out not to be genuine. Seven Sharp reporter Dan Butler also made up an abusive message.
Kenrick said he had received numerous questions today asking how a journalist and presenter of Williams' seniority and standing could have done such a thing.
"It is crucial to our integrity as a news organisation that we don't allow people to think that Peter's contribution to the news story was a deliberate falsification intended to deceive viewers.
"I have spoken with Peter at length and I understand that the invitation to him to participate suggested a similarity with a show by American comic Jimmy Kimmel that featured celebrities reading out unkind tweets.
"This led him to believe, incorrectly, that the item was intended to be comic.
"Peter had no involvement in the editorial decisions around the item and was unaware of the context until it went to air. At that point he immediately spoke up to say his contribution was invented.''
Kenrick said Williams had offered him and TVNZ viewers "his most sincere apologies''.
"This of course doesn't excuse what happened and we are taking a thorough look at our processes to ensure it doesn't happen again,'' Kenrick said.
"We'll be making sure any complaints coming to us are dealt with quickly, and the outcome of any formal complaints will be made public.''
TVNZ spokeswoman Megan Richards said the broadcaster had not received any complaints about the fabricated abuse messages today.
It was encouraging to see public support on the Breakfast show's Facebook page, she said.
"We were impressed with people's ability to see to the heart of the matter, and the intention of the original story.''
More than 150 Facebook users had commented on Facebook below a video of this morning's on-air apology, which screened shortly after 6am today.
Most were supportive, with commenters saying the presenters had made a "genuine mistake'' which was "not a big deal''.
Some commenters even said there was no need to apologise or "come clean'' about the fake messages at all.
