Eleven more women have come forward to accuse the opera star Plácido Domingo of sexual harassment, including one who alleges he groped her so hard she cried out in pain.

The new allegations come three weeks after the Associated Press reported that eight singers and a dancer had told it that they had been sexually harassed by the Spanish tenor in incidents that spanned three decades from the late 1980s.

Domingo, 78, initially described the accusations as “deeply troubling, and as presented, inaccurate”.

He added: “I believed that all of my interactions and relationships were always welcomed and consensual. People who know me or who have worked with me know that I am not someone who would intentionally harm, offend, or embarrass anyone.”

However, a singer who worked with Domingo in the Washington Opera’s 1999-2000 season has now accused him of sexually assaulting her.

Angela Turner Wilson, 48, told AP that while she had been aware of Domingo’s reputation for inappropriate behaviour, she had wanted to believe his interest in her was professional when he began sitting by her and telling her he adored her.

But one evening before a performance, she said, Domingo slipped his hands under her bra straps then reached down into her robe and grabbed her bare breast. “It hurt,” she told AP. “It was not gentle. He groped me hard.”

Wilson said she had been motivated to come forward by Domingo’s reaction to the allegations and his suggestion that “the rules and standards by which we are and should be measured against today are very different than they were in the past”.

“What woman would ever want him to grab their breast? And it hurt,” she said. “Then I had to go on stage and act like I was in love with him.”

The AP reported that several backstage employees told it that they strove to shield young women from the star as administrators looked the other way.

One woman has accused Domingo of putting his hand down her skirt and three others said he forced kisses on their lips in a dressing room, hotel room and at a lunch meeting.

A spokeswoman for Domingo accused AP of conducting an “inaccurate [and] unethical” campaign against the singer.

She added: “These new claims are riddled with inconsistencies and, as with the first story, in many ways, simply incorrect.

“Due to an ongoing investigation, we will not comment on specifics, but we strongly dispute the misleading picture that the AP is attempting to paint of Mr Domingo.”