Jared Leto was heckled by an audience member during a Q&A at the Santa Barbara film festival, who accused him of 'trans-misogyny' for his portrayal of a transgender person with Aids in the Oscar-tipped drama Dallas Buyers Club.

"You don't deserve an award for portraying a trans-woman, because you're a man," the woman continued, to which Leto replied: "Because I'm a man, I don't deserve to play that part? So you would hold a role against someone who happened to be gay or lesbian – they can't play a straight part?"

The woman complained that only straight actors ever play transgender characters, and that more trans actors should get the opportunity. Leto responded: "Then you've made sure people that are gay, people that aren't straight, people like the Rayons of the world would never have the opportunity to turn the tables and explore parts of that art," referring to Rayon, his character in Dallas Buyers Club. The audience applauded Leto's comments, and he privately continued the conversation with the woman after the Q&A.

Leto was given a Virtuoso award at the festival for his breakthrough performance, alongside June Squibb, Michael B Jordan and Brie Larson; he has already won a best supporting actor Golden Globe this year, and is tipped to win the Oscar in the same category.

There have been some other public criticisms of Leto's casting. Writing on Salon, Chelsea Hawkins said: "Given that transgender people are invisible in contemporary media, it becomes problematic that Leto is taking the role of a trans person when there are trans actors out there trying to find roles and work … the stories of under-represented, oft-ignored and misunderstood communities may be best told by the people who live those lives." She highlights trans actors such as Laverne Cox from Orange is the New Black and Independent Spirit Award-nominated Harmony Santana, and argues that they need parts like Leto's.

Paris Lees, writing in the Independent, meanwhile said "Rayon isn't a person, she's a function … For truly accurate portrayals of trans people, cast trans actors."

• Tom Shone on Leto's Oscar odds

• This article was amended on 5 February 2014. An earlier version referred to Jaret Leto's role as a transgender Aids victim. The use of "victim" is in contravention of the Guardian's Style guide on the portrayal of people with Aids.