Nelly Sued by Woman Claiming Sexual Assault After British Concert, He Denies Allegations

1:30 PM PT -- Nelly tells us, "The truth will come out, and I will be vindicated. These types of false allegations undermine real claims of sexual abuse/harassment by real victims."

He's also defending his GF, Shantel, saying she's been through enough. "I am a father to a beautiful strong woman. I was raised by a strong single woman. I love them all very much. I own my actions and take responsibility for my conduct with Monique Greene. We had CONSENSUAL sex after meeting in a club. Period. And for that I had to deal with the repercussions of my poor choice. I am repairing the trust that I broke with Shantel, I have apologized to my family and friends for the embarrassment I have caused them. And, I am committed to be a better man."

Nelly adds, "I do NOT plan on walking away quietly. I have to speak up for my family and for the real victims strong enough to come forward and face people that have actually assaulted them."

Nelly's facing new legal trouble -- a woman is suing him for an alleged sexual assault after one of his shows in England.

The woman, who's filed as a Jane Doe -- claims Nelly masturbated in front of her multiple times after the December 2017 Essex concert. We broke the story ... Nelly was under criminal investigation back in February after the woman came forward with the allegations.

In docs, obtained by TMZ, she says they met during a meet-and-greet and he whispered in her ear to stay behind. She did, but that's when she claims he dropped his pants and started masturbating while saying, "You want this d**k don't you."

Doe claims she rebuffed him several times but Nelly would not back off, and told her he wanted to ejaculate on her. She says she told him something to effect of ... "You may have more quid in your bank than I do. But this doesn't make you any more special. Pull your trousers back up and f*** off."

The woman claims Nelly got aggressive and clenched his fist -- and when she asked if he was going to hit her, he allegedly said ... "No I'm just frustrated. I'm not used to not getting my way, just do it." She claims he forced his penis into her mouth, and that's when she jumped back and was able to flee the room.

She's also suing Nelly's GF, Shantel Jackson, for calling her a liar on Twitter.

As we first reported ... Nelly and another woman, Monique Greene, reached a mutual settlement after he was accused of raping her on his tour bus in October 2017.