Network executives pulled the commercial starring full-figured model Ashley Graham over fears that it was revealing just too much cleavage.
Plus-size lingerie firm Lane Bryant was planning to air the advert this week during a break in Dancing With The Stars.
But ABC network chiefs refused to screen it, sparking claims that they were discriminating against larger models.
A source at Lane Bryant said: 'The cleavage of the plus-size model, they said, was excessive, and we don't think that's the case.
'It certainly appears to be discrimination against full-sized women.'
The 25-second advert shows Ashley in a series of poses in Lane Bryant underwear.
A voiceover says: 'Mom always said beauty is skin deep. Somehow, I don't think this is what mom had in mind.'
Lane Bryant said the Fox network also originally refused to show the ad during American Idol and insisted on the advert being re-edited.
They finally agreed to feature it during the final ten minutes of the show.
A Lane Bryant spokesman said: 'We knew the ads were sexy, but they are not salacious.
'Our new commercials represent the sensuality of the curvy woman who has more to show the world than the typical waif-like lingerie model.
'What we didn't know was that the networks, which regularly run Victoria's Secret and Playtex advertising on the very shows from which we're restricted, would object to a different view of beauty.'
A Fox spokesman insisted: 'We didn't treat them any differently than Victoria's Secret.'
ABC declined to comment.
