While Heidi Montag and Spencer Pratt never actually saw the alleged sex tape featuring The Hills Lauren Conrad and her ex-beau Jason Wahler, they insist that it did in fact exist at one point.

"It was not a rumor, that's all I have to say," said Montag during a pre-taped appearance on Tuesday's broadcast of the syndicated The Tyra Banks Show.  "From what I heard from confirmed sources is that her ex-boyfriend was going around trying to sell it."

Conrad has continuously insisted that a sex tape with her and Wahler does not exist, and has also previously alleged her much publicized ongoing tiff with Montag began when she and Pratt began spreading rumors about the alleged sex tape. 

"I didn't see it.  I never saw it," Montag told Banks about the tape.  "But I knew there was something, and I was like, 'You've got to figure it out.'  Then it came out, and it was blamed on me.  I was the only one trying to help her through the situation."

When pressed by Banks about being sure the tape exists, Montag responded, "I'm not really allowed to elaborate" -- however nothing confined Pratt.

"I know for 100% fact that it did exist -- 1,000%," he said.  "I know for a fact, and I would take a lie-detector test because I know."

While Pratt said he also never actually saw it, he insisted it once existed and added he suspects why Conrad keeps denying it.

"She can blame it on us because she wants to keep her image clean," he told Banks.  "That's fine, we're your scapegoat villains.  What are we going to do?"

During a Monday interview on American Idol host Ryan Seacrest's KIIS-FM radio show, Pratt reiterated that the sex tape did exist at one point.

"I just wanted to address something here -- there were never rumors," said Pratt.  "The bottom line is, I heard L.C. crying about this sex tape -- that Jason Wahler did have and was trying to sell -- so many times for six months, and Heidi trying to get it back with L.C..  But they never got it back.  So there's no rumors, bottom line.  Heidi never made something up.  Jason and L.C. had this, Jason was trying to sell it, Heidi tried to get it back with Lauren.  They blame Heidi once it goes public."

Despite Montag and Conrad's apparently unsuccessful attempt to recover the tape, Pratt said he knows why the footage it contained never went public.

"[Conrad's] parents called [Wahler's] parents and shut it down," he said.  "It's that simple."