During an interview in the press room after the show's best-drama win, Washington denied his involvement in a heated on-set incident in October during which he allegedly used a homophobic slur.
"No, I did not call (co-star) T.R. (Knight) a faggot," Washington said. "Never happened, never happened."
Rather than soothing the situation, his comments left Heigl seething.
"I'm going to be really honest right now, he needs to just not speak in public. Period," Heigl told "Access Hollywood" at a Golden Globe after-party. "I'm sorry, that did not need to be said. I'm not OK with it."
She called the comments "hurtful," characterizing the incident as one that should be handled privately among the show's cast and crew.
"I don't think (Washington) means it the way he comes off," Heigl said. "But T.R. is my best friend. ... I will use every ounce of energy I have to take you down if you hurt his feelings."
Knight, who said soon after the October fracas that he is gay, appeared on "The Ellen DeGeneres Show" Tuesday to discuss the original incident and Washington's recent comments.
"He referred to me as a faggot. Everyone heard it," Knight said of the October squabble.
Comments from Heigl and Washington were set to air Tuesday on "Access Hollywood." A call placed after hours Tuesday to Washington's representative was not returned.