Newstalk ZB presenter Rachel Smalley has apologised for referring to women weighing 72kgs as "heifers" and "a bunch of lardos" on air when she thought her microphone was switched off.
Smalley made the comment shortly before 6am today after she had been discussing a story that said an emergency contraceptive pill was less effective in women weighing more than 70 kilograms.
According to Bloomberg, the average weight of New Zealand women is 74.6kg.
"I deeply regret the comments. They were offensive," Ms Smalley said.
"I left my microphone on and a conversation meant for off-air, went on-air and the audience only heard one side of that conversation.
"That said, my comments were offensive. I'm sorry. It was a genuine mistake."
Auckland woman Jill Smith heard the slip-up and was appalled. She planned to complain to the Broadcasting Standards Authority.
National MP Scott Simpson said the comments were bound to upset many people.
Mr Simpson said it was probably "just a case of sloppy button pushing" rather than an intentional desire to broadcast the comments.
However it was not a good idea to make light of serious matters, he said.
The comments created a buzz on Twitter.
ZM host Polly Gillespie tweeted: "I'm a 'lardo' and Im owning it..."
The Edge radio station's Jay-Jay Feeney posted: "I weigh a bit over 72kgs. I'm what Rachel Smalley would call 'a hefer' or 'a Lardo'. #TimeToDietAgain"
It appears the audio for this part of the show is not on Newstalk ZB's website today.
Ms Smalley is host of Newstalk ZB's Early Edition and the co-host on TVNZ's Q+A programme.