It is now clear what forced CNN's hand in firing Chris Cuomo -- the guy was accused of sexual misconduct this week ... this is as he was already on thin ice.

Attorney Debra S. Katz came forward Sunday to reveal she'd been retained by a woman who wanted to go public with an allegation against the ex-anchor ... something she was apparently inspired to do after hearing about his involvement in his brother's own scandal.

She says while Gov. Cuomo's mess played out in public, Chris came on the air for his own show and said, "I have always cared very deeply about these issues and profoundly so. I just wanted to tell you that." Katz adds, "Hearing the hypocrisy of Chris Cuomo’s on-air words and disgusted by his efforts to try to discredit these women, my client retained counsel to report his serious sexual misconduct against her to CNN."

According to NYT, the woman -- who is remaining anonymous for now -- is a former junior colleague of Chris' from another network, and her claims are unrelated to Gov. Cuomo.

Katz goes on to describe how she contacted CNN on Wednesday -- a day after he'd been suspended -- to report her client's allegations against Chris ... and by Friday, she says she was already in discussions with the network to provide evidence and making the woman available for an interview with CNN's outside counsel.

She finishes by saying, "My client came forward at this time because she felt in sharing her story and related documentation, she could help protect other women. She will continue to cooperate with CNN’s investigation into her allegations. Given the nature of her allegations, she wishes to remain anonymous, and we ask that you respect this decision."