The Foreign Affairs Minister is being described as acting "like an insane man" by a senior Labour MP over his comments about former Australia Foreign Minister Bob Carr.
Winston Peters' office has confirmed it has received a letter from lawyers acting for Carr.
The letter, seen by Newshub, claimed Peters made multiple "false and defamatory" statements on RNZ regarding Australia-China relations.
Carr's legal team were instructing New Zealand lawyers to begin defamation proceedings, the letter said.
Labour MP Willie Jackson reacted to the developments on AM's Friday political panel.
"I thought it was a terrible comment from Winston," Jackson said.
"It's unbelievable the way he operates and acts.
"Let's be clear, I think we all looked at him when he was overseas and there were some people who were very proud - I wasn't surprised.
"He performed so well on the foreign stage; he gets back and he acts like an insane man, I don't know what's wrong with him - he comes into the House and just goes crazy.
"It's not personal because on the same show I've said he's a political phenomenon and I'll give him that... But the reality is, you can't do that to this guy who's given great service in terms of Australian politics and he's gone too far."
He went on to say the National Party, which leads the Coalition of which Peters' New Zealand First is a member, isn't "able to pull him up".
Appearing on the panel alongside Jackson, senior National minister Erica Stanford said the Labour MP was "on the show every week doing the same thing to most politicians, so I'm not sure we should be listening to you".
"However, I just want to say that it's the rough and tumble of politics," she said, echoing comments made by Prime Minister Christopher Luxon on Thursday.
She said Peters was doing a "phenomenal job".
"I think he's probably been to more countries in the last few months than the previous Foreign Minister did in her entire six years.
"The key is that, look, these things are said - Willie pretty much does it every week on the show. I don't think that the Prime Minister is too bothered about these comments - Winston Peters is certainly not too bothered."
