The incidents allegedly happened when Domingo held senior management positions at Washington National Opera and Los Angeles Opera.

The investigation, conducted by lawyers hired by the American Guild of Musical Artists (AGMA), concluded the accounts from 27 people showed a clear pattern of sexual misconduct and abuse of power by Domingo spanning at least two decades, according to those who spoke to The Associated Press on condition of anonymity.

In response to a request for comment from the AP, Domingo issued a statement saying: "I have taken time over the last several months to reflect on the allegations that various colleagues of mine have made against me.

"I respect that these women finally felt comfortable enough to speak out, and I want them to know that I am truly sorry for the hurt that I caused them. I accept full responsibility for my actions, and I have grown from this experience."

The union's investigation was the first of two independent inquiries launched after multiple women accused Domingo of sexual harassment and abusing his power.

The second inquiry, still ongoing, was launched by LA Opera, where Domingo had been general director since 2003 before resigning in October.

According to the people familiar with the contents of the union's investigation, lawyers from the firm Cozen O'Connor interviewed 55 people from September until late December.

In addition to the 27 who said they experienced or witnessed sexually suggestive behaviour by Domingo in the 1990s and 2000s, 12 others said they were aware of the star's reputation and that it was common knowledge at the two companies.

Union officials would not directly address the contents of the report, which has not been made public.

Most of the harassment alleged in AP's stories occurred at LA Opera and at Washington opera, which has repeatedly declined to say if it would investigate the claims.

LA Opera has not said when or if it will make its findings public.

Australian Associated Press