Phil Robertson isn't one to shy away from controversy or tow the popular line, especially where it concerns human sexuality and sex.

And a video of his recent preaching on sex and marriage isn't likely to win the Duck Dynasty patriarch any fans in liberal circles.

Robertson was sharing his thoughts on the issue a few weeks back at White's Ferry Road Church in West Monroe, Louisiana, where he and his eldest son Alan Robertson are elders, CNS.com reports.

While espousing marriage as a union between one man and one woman is often laughed off as old-fashioned or out of touch these days, Robertson didn't hold back in doing just that as he explained that God made man and woman for each other.

And in his view, the correlation between sex with multiple partners, and the prevalence of sexually transmitted diseases is clear.

"Man marries a woman," he said in his sermon for Duck Commander Mission Sunday.

"They can procreate, fill the Earth with offspring – they need to stay together just like that. You know what those two will never have?

"They will never have a sexually transmitted disease. You know why? They keep their sex between the two of them. They can't catch a sexually transmitted disease."

He continued: "Biblically correct sex is safe.  It's safe. You're not going to get chlamydia, gonorrhea, syphilis, AIDS – if you, if a man marries a woman, and neither of you have it, and you keep your sex between the two of you, you're not going to get ever sexually transmitted diseases."

But his sermon wasn't only intended to challenge modern America's social mores, but the behaviours of the Christians sitting in the pews too as he speculated that most of them had at some point been sexually immoral.

"But every last one of you have been immoral, by the way," said Robertson. "Every last one of you – there's maybe a handful in here that haven't been sexually immoral. But most of you have been."

According to figures from the Centers for Disease Control and Prevention, 110 million Americans have an STD – 59.5 million of the infections being found in women, 50.5 million in men.

The CDC lists the eight most common STDs as chlamydia, gonorrhoea, hepatitis B virus (HBV), genital herpes, HIV, human papillomavirus (HPV), syphilis and trichomoniasis.