Dr. Ben Carson, a rising star in conservative circles, on Friday compared President Obama's health-care law to slavery.

"You know Obamacare is really I think the worst thing that has happened in this nation since slavery," Carson, who is African American, said Friday in remarks at the Values Voter Summit in Washington. "And it is in a way, it is slavery in a way, because it is making all of us subservient to the government, and it was never about health care. It was about control."

Carson, a pediatric neurosurgeon who was recently hired to be a contributor at Fox News, has stoked controversy with his remarks before. Earlier this year, he withdrew as graduation speaker at Johns Hopkins University amid demands from students concerned about his controversial remarks on gay marriage. Carson had mentioned bestiality and pedophilia while arguing against gay marriage in an interview.