Dame Susan Devoy unleashed on Winston Peters at an event on Thursday night, calling him "obnoxious" and claiming he told her to lose weight.
The comments were made during the TP McLean sports journalism awards ceremony on Thursday night. It's not emerged she may have been referencing a speech made by Mr Peters in the late 1980s.
Dame Susan told the crowd Mr Peters once said she's a "bit round" and told her to walk the length of New Zealand to lose a few kilograms.
There were "gasps from the entire audience", Newsroom's Tim Murphy wrote on Twitter.
"Dame Susan Devoy, Race Relations Commissioner, tells TP McLean sports journalism awards that Winston Peters is obnoxious, that she can only be fired by the Governor-General, and that he once said of her that she was a 'bit round' and could do with walking the length of NZ to lose a few kilos... Gasps from the entire audience," Mr Murphy tweeted.
Newshub sport reporter Kirstie Stanway, who was up for an award at the event, says the content of the tweets is accurate.
A spokesperson for the Race Relations Commissioner said Ms Devoy "prefers to leave her comments as they are".
Mr Peters denies having made the comments.
"I never told her to 'lose weight', or that she was 'abit round', or that she should 'walk the length of New Zealand to lose a few kilograms,' he wrote in a statement to Newshub.
"Dame Susan Devoy’s memory is failing her. What I did say, a long time ago, prior to her walking the length of New Zealand in 1998, was meant to be a compliment.
"I said that... Susan Devoy's sporting skill was of such a level that she could beat the best in the world, even when she wasn't fit."
A corroboration of the story has since emerged from a 2011 Stuff column written by sports journalist Phil Gifford. The column places the events around thirty years ago - in the late 1980s.
In it, Gifford writes that during a prizegiving speech, Mr Peters told Dame Susan, "I have always admired enormously the fact you can win world titles while carrying so much extra weight."
Ms Devoy's mention of the Governor General's involvement in firing the Race Relations Commissioner may have been an implication that Mr Peters would have trouble removing Ms Devoy from her position.
University of Otago Law Professor Andrew Geddis says "Andrew Little (as Minister of Justice) would have to consult with David Parker (as Attorney General) before telling Patsy Reddy [the Governor General] to fire Devoy...
"It isn't enough that 'Devoy is pissing Winston Peters off."
Strain between Ms Devoy and Mr Peters is long-standing.
In 2013, shortly after she was appointed, Dame Susan said she would be keeping an eye on Mr Peters. He had recently said Chinese immigrants were turning Auckland into a "supercity of sin."
Since then, she has repeatedly called out comments made by Mr Peters, including calling Mr Peters' "two Wongs" comment "outdated rhetoric".