Opera houses should value artistry and talent above beauty in their singers, according to Renee Fleming, who sang on the Lord of the Rings films soundtrack.
Fleming said an ex-manager told her she was too heavy for roles
The US opera star said she would choose a singer with a "really beautiful voice" over a "stunning-looking woman" with an average voice.
But it "depends on the situation, the (opera) house, the singer, the artist".
Last year the Royal Opera House dropped singer Deborah Voigt from a production, saying she did not suit her costume.
Double Grammy award-winner Fleming is starring in a Royal Opera House production of Otello in London.
She admitted that a singer's appearance was a major consideration in opera casting.
"Only the singers with the most extraordinary voices can be really far out of the audience's expectation for how a character should look," she said.
"But when it's between taking an average-looking woman with a really beautiful voice versus a stunning-looking woman with a less beautiful voice, my taste would be for the better voice."
Deborah Voigt was dropped from a Royal Opera House production
In her recent autobiography, The Inner Voice: Notes from a Life Onstage, Fleming said an ex-manager told her she was too heavy for the roles she wanted after the birth of her second child.
Deborah Voigt was replaced with slimmer singer Anne Schwanewilms in last year's Royal Opera House production of Ariadne auf Naxos in Covent Garden.
"It is not just a question of how someone looks - it is also how they move on stage," a Royal Opera House spokesman said at the time.
Three months later Voigt underwent gastric bypass surgery, telling the New York Times that she had lost 45kg (100lbs) following the operation.