Taylor Momsen has explained what led to her leaving Gossip Girl.

The 30-year-old singer and former actress reunited with her Gossip Girl co-star Penn Badgley for the first time since the show's series finale in 2012 in the latest episode of Penn's podcast Podcrushed.

During the episode, Taylor, who played Jenny Humphrey in the series, opened up about leaving the popular TV show to pursue her dream career, music.

"It was a childhood thing that I got put into at two years old," Taylor told Penn, who played her on-screen brother Dan Humphrey, referring to her acting career. "I wasn't making my own choices then."

She continued, "Literally, as soon as I got to an age where I could make my own decisions, it was like a click... I woke up one morning and went, 'Wait a second. I don't have to do this? I don't have to do this other job? I can just play in my band and tour and write songs? I can just do that?' Granted, a little more complicated to get out of a television show than that, but the answer was yes."

As a result of her realisation, Taylor "uprooted and changed (her) life overnight," with the help of the Gossip Girl team who agreed to write her character out of the show.

"They went, 'Well, we can't let you out of your deal, but we can write you out of the show, so you can go on tour,'" she told Penn. "They really allowed me to follow my dream, and I'm forever grateful and thankful to them for that."

Taylor's character moved to London in the fourth season of the show to pursue her own dreams. She then made an appearance for the series finale, which featured a song from her band The Pretty Reckless.