Newstalk ZB host Leighton Smith called Jacinda Ardern a "chicky babe" during a broadcast on Wednesday.

Smith was discussing one-on-one coalition talks between the Labour Party leader and her NZ First counterpart Winston Peters, which took place on Tuesday evening.

Shortly after the 8.30am news, he invited listeners to imagine how the private discussions between the 72-year-old Peters and the 37-year-old Ardern unfolded.

Peter Meecham/STUFF Talkback radio host Leighton Smith said coalition negotiations between Jacinda Ardern and Winston Peters were between "old codger and a chicky-babe".

"How do you think the meeting between Winston and Jacinda was? What do you think?" Smith said.

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"Here's a guy of 72 with a 37-year-old chicky babe."

KEVIN STENT/STUFF Smith called New Zealand First leader Winston Peters an "old codger".

Outside the sound booth, Smith's producer doesn't seem to have been impressed by the remark because Smith's next comment was: "Yes, I know, the look of horror through the glass."

But Smith was undeterred, continuing: "But I mean, seriously, an old codger and a chicky babe. Let's just put it in the vernacular, okay? An old codger and a chicky-babe. And how do you think they - I mean, the great-grandfather, really.

"How do you think that would have gone? After all the years of experience and everything that has gone before, how do you think [Peters] would have dealt with that? Would he have dealt honestly with it? Would he have put on a show of some kind, as in, would he have played his ego down, because he's got an ego."

Smith went on to say that Peters' "nature" might have meant he put Ardern down during the talks.

"But there wouldn't have been any room for that, with the political correctness under which we all live now, he would have had to play his cards very close to his chest, or at least his emotion," Smith said. "Wonder how it went."

He said that Peters and National Party leader Bill English would have an "advantage" because of their shared experience in politics.

"And then of course there's a couple of guys who are more similar in age, although there's still a 15 or 16-year age gap, or thereabouts. But they've both been around a long time, they know how the game is played, it's to both of their advantage.

"I would imagine that there would have been some honesty in that room, some honesty and even a bit of challenge, each knowing that it was to their own advantage not to put a foot wrong."

During the election campaign earlier this year, Ardern was asked several times about her plans to become a parent - a question she answered, but one she told AM Show host Mark Richardson was "unacceptable" to ask other women.

Smith's employer NZME declined a request for comment on the gaffe. Ardern also declined comment.