The programme, which launched on Friday night, features eight pop singers learning how to perform arias for judges Katherine Jenkins, Rolando Villazon, Meat Loaf and Laurence Llewelyn-Bowen.
Royal and Welsh National soprano Rebecca Evans has claimed that the series gives a false impression of opera.
"I think it's exploiting the world of opera," she told The Independent. "They will be calling more people opera singers when they are not opera singers - it's television gone mad.
"Being an opera star is working in an opera house where you spend six weeks in a rehearsal room planning for the production. Opera singers are like athletes - you have to have stamina. It takes years of hard graft and dedication to become an opera singer. The series will give the wrong impression."
Sarah Connelly, who is preparing to appear in Ariadne at the Metropolitan Opera in New York, commented: "They do need to point out that opera isn't just about singing. That's just the start. You have to study the psychology of the character and the intention of the composer. We attempt the big questions in life and try to interpret the score on a deeper level. It's not just about getting the notes in the right order."
However, tenor Russell Watson defended the series, arguing that anything which brings to genre to mainstream audiences is a good thing. "I've been a huge supporter of popularising this genre. Long may it continue," he said.
Popstar To Operastar, which is hosted by Myleene Klass and Alan Titchmarsh, continues on Friday at 9pm on ITV1.