(Updated: November 26, 2012 at 4:33 PM CT)

A congressional hearing on autism planned for later this week is being hailed as a once-in-a-decade milestone but it’s not without controversy.

The hearing of the U.S. House of Representatives’ Oversight and Government Reform Committee is scheduled for Thursday afternoon. Lawmakers plan to address the “federal response to the recent rise in autism spectrum disorders diagnoses,” according to materials provided by committee staffers.

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In addition, the committee will also examine how government resources for autism are allocated and consider current research and treatment options.

Advocates at Autism Speaks are welcoming the hearing as a “much-needed” step, noting that the last time Congress held a similar event was in 2002. Witnesses expected to testify before the committee this week include the organization’s co-founder, Bob Wright, as well as officials from The Autism Society, the Asperger Initiative at Mercyhurst University and SafeMinds, a group which supports the idea that vaccines contribute to autism, a theory that’s widely discredited by the scientific community.

Representatives from the National Institutes of Health and the U.S. Centers for Disease Control and Prevention are also scheduled to appear.

The event faced staunch opposition, however, from self-advocates who said they were being left out of the conversation.

“The fact that in this day and age that the House majority would hold a hearing on autism and not include an autistic person in the hearing is profoundly disappointing,” said Ari Ne’eman, president of the Autistic Self Advocacy Network.

And on Monday, members of Congress appeared to acknowledge the concerns, adding two people with autism — Ne’eman and Michael John Carley of the Global and Regional Asperger Syndrome Partnership — to the list of scheduled witnesses.