Image copyright Getty Images Image caption Robertson has previously come under fire for his remarks about homosexuality

The star of the US TV reality show Duck Dynasty is facing criticism after a speech that included a graphic story about an atheist family being killed.

Phil Robertson appeared to be using the imagined story to claim that atheists would not find rape or murder immoral.

Atheist groups denounced the speech, saying it was unlikely Robertson actually knows any atheists.

In 2013, he was suspended from his TV show and quickly reinstated following derogatory remarks about homosexuality.

Robertson has since become a political figure. He recently spoke at CPAC, a large gathering of American conservatives that included presidential hopefuls such as Ted Cruz and Rand Paul.

"Two guys break into an atheist's home," Robertson said in the speech. "He has a little atheist wife and two little atheist daughters.

"Two guys break into his home and tie him up in a chair and gag him. And then they take his two daughters in front of him and rape both of them and then shoot 'em and they take his wife and then decapitate her head off [sic] in front of him."

Image copyright ITV Image caption The hit reality sitcom follows the Robertson family and their multi-million "duck-call" business

He continued: "And they can look at him and say, 'Isn't it great that I don't have to worry about being judged? Isn't it great that there's nothing wrong with this? There's no right or wrong, now is it dude?'"

Duck Dynasty - now in its seventh series - has broken several ratings records on both A&E and cable television as a whole, with the fourth season premiere drawing 11.8 million viewers.

It follows the lives of the Robertson family, a clan with old-fashioned values who live together in Louisiana, running their multi-million dollar family business, Duck Commander - which makes products for duck hunters.