The Prince of Wales said "Don't believe all that crap" when radio presenters asked him about claims that he takes his own toilet seat with him when he goes abroad.
Charles was asked the question in an interview for Brisbane's Hit105 station as he carried out an engagement in the city during a seven-day tour of Australia.
He replied: "My own what?", and added: "Oh, don't believe all that crap."
The rumour was published in a new biography, Rebel Prince: The Power, Passion And Defiance Of Prince Charles, by Tom Bower.
Clarence House said it would not be commenting on the radio station's interview.
On Wednesday, Charles's director of communications, Julian Payne, referred to the rumour on Twitter.
He wrote: "The Prince and the Duchess's tour of Australia and Vanuatu begins: 30 engagements, 7 days, 1 Commonwealth Games, 0 personal loo seats."