Lane Bryant: Networks Rejected Our Plus-Sized Models in Lingerie

Lane Bryant is trying to roll out a sexy new ad starring Ashley Graham and other plus-sized models wearing almost nothing ... but multiple TV networks have banned the spot.

TMZ has obtained the unaired commercial, which sources connected to Lane Bryant tell us was rejected by ABC and NBC. We're told neither provided specifics about what crossed the line ... other than to say they were turning it down "as is."

Our sources firmly believe it's a size issue and not nudity ... since thinner women frequently appear in commercials which are already airing. Think Victoria's Secret.

NBC says it's asked Lane Bryant to make "minor edit to comply with broadcast indecency guidelines." It would not say what specifically was indecent about the ad.

We also reached out to ABC, but so far ... radio silence.