Tony Perkins, president of the Family Research Council (FRC), is among the conservatives calling on Republican presidential candidate Ben Carson to explain his support for gay rights initiatives while serving as a director at major companies.

While serving on the boards of retailer Costco Wholesale and food manufacturer Kellogg, Carson supported several gay rights initiatives, including domestic partner benefits, diversity training and barring discrimination based on gender identity.

“I think he has to explain this,” Perkins told Reuters. “As he is pursuing the presidency, what he has to make clear is that the board positions should not be reflective of his public policy.”

Carson has been vocal in his opposition to same-sex marriage. In 2013, he compared marriage equality to bestiality and pedophilia. More recently, he said allowing gay couples to marry “negates the word of God.”

During last week's GOP debate, CNBC moderator Carl Quintanilla asked Carson about serving on the board of Costco given his apparent opposition to gay rights.

“Obviously you don't understand my views on homosexuality,” Carson responded. “I believe our constitution protects everybody regardless of their sexual orientation or any other aspect. I also believe marriage is between one man and one woman. There is no reason you can't be perfectly fair to the gay community.”

Fellow directors at Costco and Kellogg told Reuters that they do not remember Carson objecting to the policy changes.

“Ben Carson never came into the boardroom with any kind of social policy commentary,” said Jefferey Brotman, chair of Costco's board.

Carson stepped down from both boards in May.