The union that represents opera performers said Sunday it is launching its own investigation into sexual harassment allegations against opera legend Placido Domingo.

The announcement comes just days after 11 more women leveled claims against the 78-year-old tenor.

The American Guild of Musical Artists said it’s taking matters into its own hands because it doesn’t trust that individual opera companies can do enough to probe the claims.

“Given the uncertainty surrounding the investigations of our signatory companies, AGMA’s internal investigation will not be limited to conduct that occurred at a specific company or at a particular time,” the union’s executive director, Len Egert, said in a statement.

He said the union probe will also “examine the systemic failures within the industry.”

The new accusers surfaced last week, one month after eight other women came forward and claimed the multiple Grammy-Award-winner had engaged in decades of inappropriate conduct which one victim said was a “well-known secret” in the music world.

One of the new accusers, Angela Turner Wilson, said she was performing with Domingo at the Washington Opera during the 1999-2000 season when the married tenor stood behind her and slipped his hands under her bra and grabbed her breasts.

“It hurt,” Wilson said. “It was not gentle. He groped me hard.”

A spokesman for the famed tenor said the allegations were “riddled with inconsistencies” and “in many ways, simply incorrect.”

Domingo received a standing ovation in a show of support when he returned to the stage for the first time since the allegations surfaced last month — a performance of Verdi’s “Luisa Miller” at the Salzburg Festival in Austria.

He’s also still scheduled to perform in Verdi’s “Macbeth” at the Met later this month.

But several opera houses have since cancelled performances — most recently the Dallas Opera.

The Los Angeles Opera, where Domingo has been general director since 2003, is conducting its own investigation but has not disclosed any details.

With Post wires