The actress plays Jenny on the show and is named as a series regular, but has only appeared in three episodes of the current season.
Deadline claims that Momsen will begin an indefinite hiatus following the next episode.
Sources suggested that she will miss at least four instalments but insisted that the decision was taken for creative reasons rather than because of her off-screen behaviour.
The actress was described by guest star Tim Gunn as "pathetic" and a "diva" on set and has recently been criticised for smoking, carrying knives, and flashing at a concert.
Representatives for The CW and Warner Bros declined to comment.