Alec Baldwin has slammed his own brother in a letter to a leading U.S. gay magazine.

The Cooler star took offence at born-again Christian Stephen’s recent public comments on same-sex marriage, and decided to let the gay community know he doesn’t share his sibling’s beliefs.

Stephen recently called into Howard Stern’s radio show, to lend his support to former U.S. presidential wannabe Mike Huckabee’s campaign - and he added a stinging condemnation of homosexual marriage.

The Usual Suspects star said, "I don’t believe that gay marriage is in line with God’s word, which is found in the Bible… and the Bible says that gay marriage is not acceptable." Brother Alec, who also opposes his Republican brother’s political views, has responded by firing off a letter to gay magazine The Advocate.

He writes, "People like that… they want to ban gay marriage because those people are incapable of having a biological family - that’s their only argument.

"You can ban gay marriage, but if you’re going to make it fair, then you have to ban marriage for everybody else who won’t produce children. But they just single out groups of people that they hate."