MOSCOW—A prominent Russian opera star who is also a member of parliament told a meeting of the ruling party that a recently passed law banning gay propaganda was causing "colossal" damage to the country's reputation and making it harder for Russian artists to work abroad.

Maria Maksakova, a mezzo soprano soloist with St. Petersburg's Mariinsky Theater, is one of the few people in the Russian government to speak out in public against the controversial law that has been met with international condemnation.

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