The actresses - who play Vanessa Abrams and Jenny Humphrey respectively in the series about a group of rich New Yorkers - have been told they won't be returning as season regulars when the show begins its fifth season later this year although they could guest-star in future episodes.
Both stars had been increasingly sidelined in season four with 17-year-old Taylor only appearing in four episodes.
Jessica - who has previously dated co-star Ed Westwick- has found her character with little screen time recently and a recent revelation that Vanessa is set to study abroad will see her exit the series in the near future.
However, the five main stars of the show, Ed, Blake Lively, Leighton Meester, Penn Badgley and Chace Crawford, will all return for the fifth series while newcomer Kaylee DeFer will be promoted to a series regular.
Jessica, 26, is likely to focus on her movie career having just signed up for the female lead in new teen comedy movie 'Owned', about a high school student who causes trouble by trying to blackmail her neighbour, while Taylor has been spending increasing amounts of time on her band The Pretty Reckless.