The cast of One Tree Hill have released a joint letter detailing the show's traumatising "open secret".

For more than 10 years, One Tree Hill, a TV show that followed the drama of a group of teens growing up in a fictional town of North Carolina, dominated the ratings.

Now, cast members – including the show’s female stars Sophia Bush, Hilarie Burton and Bethany Joy Lenz – and crew have alleged they faced years of sexual harassment at the hands of the show’s former showrunner, Mark Schwahn.

In an open letter, first published on Variety, 15 women said that Schwahn’s behaviour was “something of an ‘open secret’ during filming”.

“Many of us were, to varying degrees, manipulated psychologically and emotionally,” the letter continued.

"More than one of us is still in treatment for post-traumatic stress. Many of us were put in uncomfortable positions and had to swiftly learn to fight back, sometimes physically, because it was made clear to us that the supervisors in the room were not the protectors they were supposed to be.

"Many of us were spoken to in ways that ran the spectrum from deeply upsetting, to traumatising, to downright illegal.

"And a few of us were put in positions where we felt physically unsafe. More than one woman on our show had her career trajectory threatened."

The cast and crew said that they were told if they went public with the claims against the showrunner, One Tree Hill would be cancelled and "hundreds of lovely, qualified, hard-working, and talented people" would lose their jobs.

The cast and crew were inspired to pen the powerful letter after one of the show's writers, Audrey Wauchope, shared on Twitter she had been subjected to "frequent and unwanted touching" during her time on the show.

"Female writers would try to get the spot where the showrunner wouldn't sit as to not be touched," she wrote.

"Sometimes we wouldn't luck out and he'd just squeeze his disgusting body in between us and put his arms around us, grinning.

"He pet hair. He massaged shoulders. I know he did more but not to me so they're not my stories to share."

Wauchope also alleged the showrunner - who she did not name but many deduced to be Schwahn - also shared naked pictures of an actress he was dating without her knowledge and skipped the studio's mandatory sexual harassment meeting.

I'm furious and sad and everything else for the women who have sat on that couch next to that man. And I'm furious and sad and everything else that years later I don't feel safe to be able to do anything real about this and that it seems to be happening all over this town.

— Audrey Wauchope (@audreyalison) November 12, 2017

I write all this to say that there are trickle down psychological effects to all this bullshit and the town is littered with the collateral damage of abusers who have been given free reign. If you're sitting on one of these staffs please know whatever you are feeling is real.

— Audrey Wauchope (@audreyalison) November 12, 2017

Since Wauchope's allegations and the letter from female cast and crew went public, the male stars of the show have also begun to respond.

"The women of [One Tree Hill] have always been strong and incredible," Chad Michael Murray said in a statement to EW.

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"Today they’ve made us all even more proud by standing as a beacon of what is right, and continuing to lead & change the atmosphere of society.

"It's an honour to see all women stand up to the opposition that has caused so much pain. Equal rights & equal treatment isn’t an option, it is mandatory. Equality, safety and respect for all is the goal.

I stand with all the those who have suffered... OTH Women- I'm so dang proud of you."

Much love to our brother bear #LeeNorris, who has always been supportive. He's one of the good ones too. #BurnItDownSis pic.twitter.com/HGzzbrzhKF

— Sophia Bush (@SophiaBush) November 14, 2017