UPDATED 1:29pm: A media commentator says news bosses need to accept ratings will rise and fall instead of panicking and changing formats.

TV3 has confirmed it's cutting its Sunday night news bulletin in half to 30 minutes.

The decision comes as the nightly current affairs show Campbell Live is under review.

Media commentator Josie Pagani argues TV companies need to change the way they think about current affairs.

"TVNZ and TV3 are both scared of news. Their reaction to dropped ratings is to go - news doesn't rate so we've got to replace it with reality TV and we've got to replace it with soaps."

Pagani says the format shift isn't as big an issue as the lingering uncertainty over the future of Campbell Live.

"On Sunday there's not much news anyway, so maybe moving it to half an hour isn't such a major issue."

Media commentator Brian Edwards says the shape and content of the new 30 minute long bulletin, cut down from an hour, will determine its success.

"You keep finding out about the weather at the beginning and the middle and the end...you just wonder how much actual news you can put into a half hour when you take all those other bits and pieces into consideration."

More than 60,000 people have signed a petition calling for TV3 to retain Campbell Live.

The current affairs show has a guillotine above its head, with a daily soap among the possible replacements if it goes.

Along with petitions, a Facebook group has been created urging TV3 bosses to keep Campbell Live and people are also writing to them directly.