The son of former president Ronald Reagan says legalising equal marriage will lead to “polygamy, bestiality and perhaps even murder.”

“It’s ultimately about changing the culture of the entire country,” Michael Reagan wrote in an article for the Ironton Tribune.

The 68-year-old slams the Republican Party, saying party leaders are too preoccupied with the next presidential election to be concerned about the issue.

“I don’t expect the GOP to provide any leadership. Republicans are too busy cat-fighting with each other and making sure their presidential choice will be whooped by Hillary Clinton in 2016.

And where in the heck are the churches on the issue of legalising gay marriage?

Where are the Protestants, Jews and Catholics? Have they lost their tongues? Their hearts and wills? Their institutional you-know-whats?

Where’s the moral outrage? Why aren’t thousands of our pastors, priests and rabbis shouting from their pulpits? Why aren’t they leading their congregations through the streets in mass protest?

Why aren’t their bishops appearing on the tube with David Gregory and Piers Morgan to defend the institution of marriage as a union of one man and one woman?

Like the bank executives who are too chicken to stand up to the federal bullies in Washington, and like the energy company bosses in California who won’t stand up to the Green Socialists in Sacramento, the churches cower in fear.”

Last week, the US Supreme Court heard two major cases related to equal marriage, one challenging a California ban and the other challenging a federal law restricting tax and other marriage benefits to opposite-sex couples only. The court is expected to issue rulings in June.

Referencing the cases, Reagan added: “This fight over Proposition 8 isn’t just about saying it should be legal in the eyes of government for two people of the same sex to get married in California.

“It’s ultimately about changing the culture of the entire country; it inevitably will lead to teaching our public school kids that gay marriage is a perfectly fine alternative and no different than traditional marriage.

“There is also a very slippery slope leading to other alternative relationships and the unconstitutionality of any law based on morality. Think about polygamy, bestiality, and perhaps even murder.”