Osbourne, 61, claimed on "The Graham Norton Show" last month she had an "excruciating" procedure to have her "vagina tightened."
However, she told Stern Wednesday the story was a "flippant, stupid thing to be silly," UsMagazine.com reported.
"I feel like you did [get the surgery] and now you're embarrassed to say it," Stern said.
"I made it up," Osbourne insisted.
"You're saying you fabricated the whole thing?" Stern asked.
"I swear on my children's lives I made it up -- just to be flippant," she replied. "How could I do that after I've had so much like, ill health? Now I'm going to start putting scaffolding up my vagina?"