Supermodel Kate Upton has spoken speak out against how Guess is handling sexual misconduct investigation against co-founder Paul Marciano.

The model took to social media to share another statement, slamming Guess chiefs for being biased and claimed that the internal investigation is a "stunt". She captioned the post on Instagram and Twitter saying, "Let's make true change happen! #metoo #TRUEchange."

A post shared by Kate Upton (@kateupton) on

She started by saying, "I just learned that Guess hired Paul Marciano's PERSONAL lawyer to run their internal 'investigation. I'm truly disheartened to learn that Guess is treating this abuse of power and sexual misconduct (to multiple women) in such a manner."

Upton had accused company co-founder Marciano of harassment and assault, claiming he groped her breasts and made inappropriate comments to her during meetings and photoshoots in 2010 and 2011.

She continued, "I shared my story to help create long-term change at the highest levels of the industry and corporate ladder. I also wanted to empower others to share their stories to stand up for change – whether as a victim of or as a witness to this behaviour."

Upton called the investigation a "stunt" and revealed that she has refused to participate as a witness in the inquiry. "Hearing how this 'investigation' is being conducted, and also knowing a strong fear of retaliation still exists within Guess' corporate offices, is extremely disappointing and upsetting."

"To conduct an investigation like this seems like a stunt, and is a clear indication to me that Guess is not taking these claims seriously, nor are they committed to making changes at the highest level. Until Guess makes a commitment to conduct an unbiased investigation, I have declined to participate.

"I look forward to participating if and when Guess retains a truly independent firm to run the entire investigation."

Upton came forward on Twitter earlier in February, accusing Marciano of "sexually and emotionally" harassing women in a series of tweets. "It's disappointing that such an iconic women's brand @GUESS is still empowering Paul Marciano as their creative director #metoo," she wrote at the time, later sharing the same message on Instagram.

Following this, Marciano denied all claims of sexual misconduct against him and stepped down from the fashion house as investigators conduct their review.

He announced in a statement, "I have pledged my full co-operation to the company, and I have the utmost confidence in our chief executive officer, Victor Herrero, to continue leading the company during this time".