The heated controversy at ABC's top show, "Grey's Anatomy," boiled over Thursday as the network rebuked co-star Isaiah Washington for an anti-gay comment and Washington issued a lengthy apology.

"We are greatly dismayed that Mr. Washington chose to use such inappropriate language at the Golden Globes, language that he himself deemed `unfortunate' in his previous public apology," the network said in a statement.

"His actions are unacceptable and are being addressed," the statement conclude.

During a backstage interview Monday at the Globes gala, Washington denied involvement in a heated on-set incident in October during which an anti-gay remark was reportedly uttered.

"No, I did not call (co-star) T.R. (Knight) a faggot," Washington told reporters. "Never happened, never happened."

In his apology Thursday, Washington acknowledged "repeating the word Monday night."

"I apologize to T.R., my colleagues, the fans of the show and especially the lesbian and gay community for using a word that is unacceptable in any context or circumstance. I marred what should have been a perfect night for everyone who works on `Grey's Anatomy.' I can neither defend nor explain my behavior. I can also no longer deny to myself that there are issues I obviously need to examine within my own soul, and I've asked for help."

ABC said in its statement it has "a longstanding policy to maintain respectful workplaces" for its employees, adding that the network had "dealt with the original situation in October, and thought the issue resolved."

The statements came a day after the president of the Gay & Lesbian Alliance Against Defamation demanded an apology from Washington. On Thursday, GLAAD President Neil Giuliano said he was encouraged by Washington's latest remarks.

"We are ... optimistic that it may mark a turning point in this deeply troubling situation," Giuliano said.

Washington said Thursday he welcomes the chance to meet with gay and lesbian community leaders "to apologize in person and to talk about what I can do to heal the wounds I've opened."

"I know a mere apology will not end this, and I intend to let my future actions prove my sincerity," Washington said.

Knight, who said soon after the October fracas that he is gay, appeared in Tuesday's taping of "The Ellen DeGeneres Show" to discuss the original incident and Washington's recent comments.

"He referred to me as a faggot," Knight said of the October incident. "Everyone heard it."

"Grey's Anatomy," now in its third season, won the Golden Globe for best television drama. It regularly finishes atop or near the top of the Nielsen rankings.