Shares of Guess are falling after Kate Upton accused company co-founder Paul Marciano of sexual misconduct on social media.

In a tweet and a post on Instagram Wednesday, the model and actress writes, "It's disappointing that such an iconic women's brand @GUESS is still empowering Paul Marciano as their creative director."

She added the hashtag #metoo, thrusting her into the movement that has spread virally after public reports of sexual harassment allegations against movie mogul Harvey Weinstein.

Guess, based in Los Angeles, couldn't be immediately reached for comment.

Paul Marciano and his brother Maurice co-founded the brand in 1981, redefining the denim business. The brand is now selling in over 80 countries.

Guess shares fell nearly 15 percent, or $2.74, to $15.63 in trading Thursday.