The former boss of Close Up is certain the network will replace the current affairs show with a "light and fluffy magazine" programme, driving viewers to the competition.
Bill Ralston, who was head of news and current affairs from 2003 to 2007, said TVNZ was on "a quest for ratings" and would replace the hard-hitting show with something more populist.
"They'll just do anything for money and they think they can get more ratings out of a far less serious or intelligent product than Close Up currently is. All they'll do is shove more audience to John Campbell, who's doing some fairly serious current affairs material."
The current boss of TVNZ news and current affairs, Ross Dagan, said the network wanted to reinvent the early evening slot "to present the stories of the day in a way that is very different to what has gone before".
"Everyone on the show is aware that traditional current affairs formats are losing favour with audiences, and this team has set the bar for what's possible.
However ... the company's view is that this format has simply run its course."
It is understood it was a struggle to sell ads in the Close Up slot and there was pressure on Mr Dagan to reinvent.
There has been speculation that the new programme would be a talk show with a mix of news and entertainment. Mr Dagan was behind The Project - a primetime show in Australia hosted by comedians presenting news stories.
Programming head Jeff Latch would not be drawn on the talk show idea but said: "It will remain in news."
Mr Dagan told staff in a confidential email that the live studio crew used for the show would not be affected by the proposed changes.
Paul Holmes, the first current affairs host to hold the timeslot in 1989, said adding entertainment to the mix would not mean moving away from information.
"There might be need for a greater unpredictability. The essence of gathering a crowd is unpredictability."
He believed New York correspondent Jack Tame would be a good choice as a host for the new show.
Mark Sainsbury, the host for six years, said his role would disappear with the show - ending a 31-year career at TVNZ.
Last night outside TVNZ headquarters, he said he would miss the job.
"I can't think, woe is me. Journalism is a great profession. I've done this show, political editor, foreign correspondent, I've had opportunities you wouldn't get otherwise.
"Not everyone likes your style or what you do. You put yourself out there, and you have to take it."
His last day is November 30.
Next in line?
Corin Dann: Did well on Breakfast and has serious news credentials. Current political editor of One News.
Pippa Wetzell: Dubbed the mother of the nation in waiting, popular with viewers and TVNZ bosses alike.
Mike Hosking: Current stand-in, strong interviewer but not to everyone's tastes.
Pam Corkery: Long-time broadcaster and former politician, now back on radio.
Paul Henry: A populist choice, but loose-lipped.
Jack Tame: Young but popular with viewers.