Pauly D's got his work cut out for him with his new baby mama -- so claims the daddy of her 1st child ... who has some serious words of warning for the "Jersey Shore" star.
Meet 33-year-old Lance Gerbino, the father of Amanda Markert's 5-year-old son. His friend just posted this video on Instagram, where Lance calls Amanda a crazy "drug addict stripper" -- something she strenuously denies.
Lance is no angel himself -- as we reported, one reason Pauly wants full custody is because there's a felony drug arrest warrant out for him, and he thinks there's a danger if Lance comes in contact with the baby.
As for Amanda, her lawyer tells us, "Amanda is an extremely wholesome young lady who is goal oriented." He adds she's never been a stripper and has absolutely no drug issues.
BTW ... Lance's friend has taken the video off Instagram.