Veteran broadcaster Peter Williams and Seven Sharp reporter Dean Butler read out the fabricated messages as part of a segment on the early morning show, hosted by Rawdon Christie and Alison Pugh.
The segment, which also featured eight of their colleagues reading out abusive messages, dealt with online bullying and abuse after the death of television personality Charlotte Dawson.
This morning during the show, Christie and Pugh apologised for the pair's actions.
"We told you they were all genuine, we believed they were all genuine. Our intention, to highlight how serious this type of bullying is, and that all walks of life can be on the receiving end," Christie said.
"Even though they could have taken their pick from genuine viewer abuse, Peter Williams and Dean Butler read aloud messages that hadn't come from our viewers.
They had simply misunderstood what we were doing and thought they had been asked to provide for a light-hearted parody," Pugh said.
"The guys are mortified about what's happened there, obviously so are we.
"It was wrong, we apologise and we must stress that all the other messages were genuine," Christie said.
The pair's on-air apology was similar to the one issued by TVNZ head of news John Gillespie last night.
"Even though they could have taken their pick from genuine viewer abuse, Peter Williams and Dean Butler misunderstood what they'd been asked to provide and read aloud messages that hadn't come from our viewers," he told the Herald.
"They mistakenly thought they had been asked to contribute to a send-up. The guys are mortified about what's happened and so are we. Those two messages should never have gone to air in what was a serious story meant to draw attention to online abuse. It was wrong and we apologise."
The other TVNZ reporters and presenters who read messages on the segment were Toni Street, Jesse Mulligan, Ruth Wynn-Williams, Nadine Chalmers-Ross, Brooke Dobson, Matt McLean, Helen Castles and Wallace.
Pugh said TVNZ was "taking this matter seriously and will be dealing with it appropriately".
Media commentator Brian Edwards said the incident might have been an "error of judgment"on their part, but was unacceptable.
"It's inexplicable that people like this who have reputations that require them to be absolutely honest and above board as a newsreader ... I just find that extraordinary that they would do that," he said.
Lifeline chief executive Jo Denvir said she feared the fabricated messages might trivialise online bullying and suicide.
"It is a very real phenomenon - you don't actually need to make anything up," she said.
"Possibly they thought they were doing the right thing, but for those of us who work with suicide every day or the repercussions on families or people affected by suicide, this is not something that should be tampered with by making things up."
