Asked if Dame Susan made it up, Peters said her memory was failing her.
"All I said is that her level of skill was of a magnitude that she could beat the best in the world when she wasn't fit," Peters said.
Sportswriter Phil Gifford said he remembered Peters calling Dame Susan overweight.
Gifford told Fairfax yesterday that Peters called her "a stone overweight", yet still able to win world titles, in a speech at a sports awards function in Auckland in 1987.
Peters said he did not recall saying that she was a stone overweight, but he and Devoy had met and worked together several times since the comments were made and they had never discussed the matter. The words "a bit round" were words he would never use.
Dame Susan has not commented on the reports of what she said, which was tweeted by Newsroom's Tim Murphy.
Peters is taking legal action against Murphy for his alleged role in the publication of his superannuation details. He said Murphy was acting for his own "perverse reasons around a campaign which he is conducting, which is bound to fail".
A spokesperson for the Race Relations Commissioner declined to elaborate yesterday, saying Dame Susan "prefers to leave her comments as they are".
Peters has made similar comments before about the weight of two women MPs, National deputy leader Paula Bennett and former Maori Party co-leader Dame Tariana Turia.
Asked about any previous references at his press conference at Parliament, he denied it and said: "No, no, sorry you can't provide one fact, can you?"
Hansard shows that Peters' references were both during Question Time and that both women hit back at Peters, one in reference to his "drinking behaviour" and the other in reference to his age — 72.
In November 2003 he questioned Turia about Maori obesity. When she said he had no evidence, he said the evidence was herself.
Turia responded: "I do not think I need to account to Mr Peters for my eating habits; nor do I expect him to account to me for his drinking behaviour ..."
Last year when he suggested Paula Bennett had been at the "local deli" rather than the coalface of her then work as Social Housing Minister, Bennett responded: "It is probably the rest home that you should be in."
There is bad blood between Peters and Devoy. In 2014 Devoy was critical of Peters making a joke about "two Wongs don't make a right" when he launched his party's immigration policy and signaled his intention to crack down on foreign ownership of New Zealand land.