In a new interview with Business Insider, Denberg details multiple accusations against Schneider -- including the claim he showed her porn and initiated phone sex when he was the head writer of "All That" -- where she was a cast member between 1994 and 1998.

Denberg says this all started around her 19th birthday ... when she says Dan invited her to a meeting and showed her porn clips -- including one scene where a woman performed oral sex on a donkey. FWIW, similar claims over the porn were also made on 'Quiet on Set.'

LBD says their relationship turned sexual after that ... as she began having sleepovers at DS's house, where they would give each other massages and watch porn. Denberg claims Schneider once fondled and put his mouth on her breasts after she lost a bet while watching "Jeopardy!" together.

She added ... "I couldn't have been more green. I couldn't have been more vulnerable."

Denberg went on to describe her relationship with Schneider as a "weird, abusive friendship," claiming he would yell at her and force her to hide a gun in her skirt on different occasions.

Schneider has responded to Denberg's allegations, slamming them as "wildly exaggerated and, in most cases, false." He tells TMZ ... "As I have previously stated, there were times, particularly in the early years of my career, that I made mistakes and exhibited poor judgment as a leader. If I did that with respect to Lori Beth, I sincerely apologize to her. But I cannot apologize for things I did not do."

He also slammed the writer of the Business Insider article, Kate Taylor ... pointing out that she's also an executive producer of 'Quiet on Set.'