Winston Peters has twisted the knife over the MediaWorks' sale of its television division, as he rallied against the media in front of party members.

The New Zealand First party's members are meeting in Christchurch this weekend for their annual conference.

Opening the event with a speech that also criticised the National Party, and Labour and Greens policy, Peters took a dig at the media, saying it had written has party off in the past.

"It was announced yesterday certain sections of them are going and are they shocked?" he said to a cheer from some in the crowd and an "aw" from others.

"Now I'm sorry for some of them because they deserve to say, but for some of them: good riddance."

New Zealand's media landscape could be set for a seismic shift as MediaWorks puts its TV arm and Auckland headquarters up for sale with no obvious buyers or Government intervention in sight.

Up to 520 jobs hang in the balance at the cash-strapped, 29-year-old broadcaster, which was once worth $700m on the stock market.

As audiences steadily pick up new viewing habits with streaming service options in abundance, and what it says are inequities with its rival TVNZ, MediaWorks has effectively been fighting on two fronts and losing ground in both battles.

Advertisers have seen the viewing changes and jumped; spending in the digital realm has increased from $366m in 2012 to $899m in 2018.

MediaWorks bosses have ruled out a sudden closure of its flagship channel, Three, which screens Newshub's 6pm news, The Project and The AM Show, which is simulcast on its radio station Magic. It also owns Bravo, a "pure entertainment" channel known for reality shows, and ThreeLife, a lifestyle-focused channel.

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But this week MediaWorks axed or reduced several shows including 7 Days and Married at First Sight NZ. The Project host Jesse Mulligan said Three might have no choice but to shut down if the Government doesn't change its broadcasting policy.

Media commentators said the TV business was worth "zero" and it was difficult to see who would take it on.

The sale is the latest blot on the media landscape in this country.

Stuff was also put up for sale this year but Australian owner Nine put that on hold after it failed to get a satisfactory bid.

TVNZ is on course for a $17m loss this financial year.

The announcement left MediaWorks staff reeling.

It is understood they found out about the plans six minutes before they were made public.

TV presenters were called to one-on-one meetings, though some of the network's biggest names are away. Newshub Live at 6 anchor Mike McRoberts is in Japan for the Rugby World Cup and Samantha Hayes is on maternity leave.

Former 6pm news anchor Hilary Barry, who spent 23 years at MediaWorks, said she was "incredibly sad and concerned" for her former colleagues.

"There are so many talented and genuinely wonderful people there. I just want to give every one of them a giant hug," she tweeted.

MediaWorks chief executive Michael Anderson also dismissed any suggestion that the announcement was an attempt to force the Government's hand over regulations governing TVNZ.

"I actually feel quite angry about such statements.

"We would never put our staff in a position where we were just bluffing and putting them through the uncertainty they're going through."

TVNZ, whose profit nearly halved in the year to June, has stopped paying dividends to the Government.

The Government is looking at its options to strengthen public media, which could include making TVNZ advert-free — allowing MediaWorks to pick up leftover ad revenue.

Asked if it was a level playing field, Prime Minister Jacinda Ardern said yesterday: "This Government is not putting funding into the day-to-day operations of TVNZ and I think that's important to keep in mind."

he said there was a place for a public broadcaster in New Zealand, and the Government was strengthening public broadcasting.

"We need to have a strong fourth estate.

"We need to have a strong media to hold to account both political agents, but others as well."

Commerce Minister Kris Faafoi has said work would be unveiled before the end of the year, and would not be fast-tracked as a result of the MediaWorks' sale.

Media agency veteran Alex Lawson said he could not think of anyone who would want to buy MediaWorks' TV assets.

Lawson, the general manager at Carat, said the obvious choice would be another media company, but he couldn't think of a local player with the means or appetite to fork out for the business.

"It's a really tough sell. It would have to come from abroad.

"Maybe another international private capital group or an Australian broadcaster?"

Former MediaWorks head of news Mark Jennings said the TV business was worth "zero".

"I don't think anybody's going to buy it, but somebody might take it off their hands if they can see a way forward."

He believed MediaWorks was genuine in putting its assets up for sale.