Lance 'Un' Rivera Disses Jay-Z for Leaving Damon Dash Broke & Dusty

Jay-Z can add yet another Chatty Patty to his list to address when he releases new music ... Biggie's former business partner is holding him partially accountable for the downfall of Damon Dash!!!

Veteran music exec Lance "Un" Rivera recently sat down for a lengthy interview with "The Art of Dialogue," where he scolded Jay-Z for his intense separation from Dash after they built the Roc-A-Fella Records legacy that sparked his mega-stardom.

Un labels Jay's behavior "sucka s***" -- an absolute put-down from their era, but goes even further and speculates that The Notorious B.I.G. would never leave him hanging like Jay did Dame. Damn!!!

As we've been reporting, Dash is in dire straits -- the mogul owed the state of New York millions of dollars and is currently promoting an artist he dubbed as the "White, Lesbian Aaliyah" ... so, yeah.

Un and Jay have a spotty history, sparked by Un being on the receiving end of the 1999 nightclub stabbing incident, which led to the Roc Nation boss serving 3 years of probation ... but Un tells the podcast it wasn't Jay who actually did the piercing.

Un says the Jay-Z fight was over rapper Charli Baltimore, who likely will be returning to the media space now that her name has been brought up!!!

Cam'ron, who was signed to Biggie and Un at the time, has also named Charli -- not bootlegging -- as the reason for the club clash.

He also alludes to having a hand in the creation of Nas' iconic Jay-Z diss track "Ether" -- and also saves some shots to send in his rival exec Steve Stoute's direction. Platinum producers Poke and Tone of the Trackmasters also got half a bar.

Jay-Z mentioned Un on Memphis Bleek's ghost hit "Dear Summer," where he rapped, "Sorry Lance, I'm just trying to advance my quotes / I ain't making you the butt of my jokes" -- and Un warns everyone not to be mad when he starts repaying the favor with his projects!!!