A Fox News radio host has refused to apologise after causing controversy by tweeting that legalising equal marriage across the US could lead to the legalisation of bestiality.

Todd Starnes was challenged on his stance on the issue by colleague Alan Colmes, and said he “absolutely” believes that liberals wanted to “destroy the fabric of the American family”, and went on to link equal marriage to the spread of venereal diseases.

On Colmes’ show, on 27 March Starnes said: “I really do believe that the agenda of the left is trying to destroy the fabric of the American family. I really do. … I absolutely believe that.”

Colmes then asked Starnes about the tweet he sent claiming that the legalisation of equal marriage would lead to the legalisation of bestiality.

Starnes defended his position, saying: “You know it’s interesting because the passage of the Bible that people — that people talk about in regards to, you know, the act of homosexuality, it goes further to talk about that. That men should not lie with beasts. And the women should not do that either. All this kind of stuff.

“I think the point I was trying to make there is that once you decide, you know what, marriage is not just between a man and a woman anymore, well, why are — you know, if you open it up, where do you draw the lines? Where do you draw the lines?”

After Colmes said that allowing equal marriage would reduce the number of cases of sexually transmitted diseases, as “marriage promotes monogamy”, Starnes said there was a breakdown in the moral compass of the US.

When he was asked if he thought it was immoral for same-sex couples to be allowed to marry, he said “that’s not my call”, and went on to say: “I’m beginning to be in the minority”, on the issue of marriage equality.

He then claimed that Christians, had become “second-class citizens” in the US. He said: “I think there’s evidence there to suggest that, yes, Christians, people of faith who oppose gay marriage are, in fact, going to be treated differently in this country. And I think that’s a bad thing.”

Starnes who appears on Fox News as a correspondent, as well as hosting his own show, has spoken out in the past against LGBT rights.

Fox News radio host Todd Starnes last week noted that the University of Tennessee intended to spend $20,000 (£13,200) on a six-day Sex Week event, which included events on topics from sexual pleasure to how UT can tackle sexual assaults.

Starnes used the headline: “University of Tennessee Uses Student Fees to Host Lesbian Bondage Expert,” which led to the university promising it would not fund the event.

He yesterday tweeted Fox News host Bill O’Reilly, saying: “Thank you, Bill O’Reilly for running all of my culture war stories this week!”

Fox News presenters Megyn Kelly and Bill O’Reilly this week surprised viewers by arguing that those opposed to equal marriage, including Tony Perkins of the Family Research Council, had no strong arguments against it.