For Answers in Genesis CEO and President Ken Ham, the reason why fewer millennials are worshipping in American churches is because of the widespread acceptance of same-sex marriage.

In his blog post, Ham said "something is wrong" when once-active churchgoers are now embracing a secular world view and lifestyle and are "rejecting all semblance of Christian belief and values."

"Most churches, it seems, are full of Christian parents, Sunday school teachers, and pastors who tell similar heartrending stories. They just can't believe what's happening," he said.

American millennials, or those born between 1982 to 2000, have either completely lost or compromised their Christian faith, said Ham, because they would much rather adhere to the broader beliefs of society.

"I believe this is a huge warning sign to the church. When a generation no longer builds its worldview on the foundation of the absolute authority of God's Word, the new generation begins to question everything it says, including its morality," Ham said.

He also pointed out that there is a "crisis in leadership" in Christian homes today, with fathers refusing to take charge and mothers forced to step up in lieu of their leadership. But Ham said this is wrong. He likened the situation to Adam allowing Eve to take charge as she is being influenced negatively by the serpent to commit sin.

"Our whole Western world is changing. But really, it's the failure of so many Christian homes and churches who have not understood the times, have not stood uncompromisingly on the authority of the Word of God, and have not trained the coming generations in the Christian worldview," Ham said. "Who has the courage to stand up and challenge homes and churches concerning the reality of what has been happening to generations of children and now the dramatic changes in the 20s generation?" he asked.