Lucy Flores claimed Friday she was beside the stage awaiting her turn to speak at a political rally when Biden put his hands on her shoulders from behind, then leaned in and smelled her hair.
"I was mortified," Flores, 39, told the New York magazine. "He proceeded to plant a big slow kiss on the back of my head," she added.
"My brain couldn't process what was happening. I was embarrassed. I was shocked. I was confused," and "I wanted nothing more than to get Biden away from me," she added.
"Even if his behavior wasn't violent or sexual, it was demeaning and disrespectful.”
The accusation might impact Biden's decision to officially enter the presidential race. Biden, 76, could announce his plans in April, Press TV reported.
The former vice president’s spokesman Bill Russo said Friday that Biden was "pleased" to support Flores's candidacy, but does not recall the incident.
"Neither then, nor in the years since, did he or the staff with him at the time have an inkling that Ms Flores had been at any time uncomfortable, nor do they recall what she describes," Russo said in a statement.
The accusations against Biden come despite his high-profile speeches about sexual assault and violence against women.
Biden's overly familiar approach with women has been a subject of controversy for years.
He has had a reputation for awkwardly touching the wives, mothers or daughters of senators during swearing-in ceremonies, and he came under criticism for massaging the shoulders of then defense secretary Ash Carter's wife in 2015.
Biden's behavior is receiving renewed attention in the #MeToo era, when the movement against sexual assault has led to the downfall of dozens of politicians, entertainment figures and businessmen.
At a Democratic Party dinner in Delaware this month, he acknowledged how his physical style has raised questions.