The maker of Stacker 2 filed a lawsuit Thursday claiming Gannascoli hasn't been doing enough to promote the product after receiving about $316,000 from the company over the last 2 1/2 years.
"He was very difficult to work with all the time," Robert Occhifinto, president of Sussex County-based dietary supplement maker NVE Pharmaceuticals, told The Star-Ledger of Newark for Friday's newspapers.
Gannascoli, 47, disputed the company's claim, which came after a tough few episodes for his character, Vito Spatafore, who was beaten to death after his secret homosexual life was discovered.
"I begged them to do things but they wouldn't," he told the newspaper. "They didn't like I was doing the gay thing" in his TV role.
Last month, Gannascoli signed with another company to endorse a competing diet pill.