The centre-back joined Bayern Munich towards the end of the transfer window for around £21m, and the Moroccan defender claimed that he was sold against his wishes by the Italian side.
However, Pallotta has angrily denied that was the case and slammed his former player as "poisonous".
He told Roma's official website: "Mehdi Benatia has obviously continued with his pattern of outright lies over the last couple of months. We had a verbal agreement on compensation and a raise back in July in Boston. He personally said to me that he was happy after I told him flat out with no exceptions that we wanted him to stay.
"Over the following month he lied about wanting to stay and about the details of his compensation to both [coach] Rudi Garcia and his teammates. Lying to me was one thing which I can somewhat handle. Lying to Rudi Garcia and his teammates was completely unacceptable to me.
"I told [sporting director] Walter Sabatini he was becoming poisonous and I wanted him gone, and Rudi and Walter agreed. It wasn't about the money; it was about having character in our locker room. We are in a very sound financial position."
Bayern were forced to move for Benatia when Javi Martinez was ruled out with a serious knee injury.