In just two years, the number of Americans who think Christians face growing intolerance and persecution in the United States has increased significantly, according to a recent poll.

In the LifeWay Research survey, 63 percent of the 1,000 respondents say they somewhat and strongly agree that Christians increasingly are confronted with intolerance, an increase from 50 percent in 2013.

Those who strongly agree with the statement are 38 percent from 28 percent in 2013.

On the other hand, 60 percent said religious liberty is on the decline in the U.S., an increase from 54 percent in 2013.

The same survey showed that 43 percent believe that American Christians "complain too much about how they are treated," up from 34 percent in 2013, according to the Washington Times.

The survey result was published on March 30 and had an error margin of 3.6 percentage points. It was conducted after the U.S. Supreme Court legalised same-sex marriage in June last year.

The landmark Supreme Court ruling immediately ignited a debate on religious liberty and discrimination.

According to Greg Jao, director of campus engagement and vice president of InterVarsity Christian Fellowship, increased media attention on the issues could be skewing the numbers in the short run.

"Because of the high media attention on a couple of key cases, I think Christians are more aware and feel more persecuted or less tolerated than they did before," he said.

He said the U.S. is "re-evaluating the privileged place that religion had in its past."

"A couple of decades ago, for instance, universities were delighted when we started a chapter, because we were considered a moral and calming influence on campus excess," he said. "They thought it was excellent — they needed help leavening the party culture. Now, of course, Christians are no longer considered to be morally virtuous additions to a community. I think Christians are actually considered moral problems to solve, particularly because of human sexuality issues."

Faith Driven Consumer founder Chris Stone said the survey reflects an increasingly influential progressive movement that campaigns for diversity yet excludes Christians.

"As the diversity-inclusion movement grows, and more and more companies become diversity-centric, what you really begin to see is a glaring gap that exists. As a Christian, you begin to see that you're being excluded from the culture, excluded from the conversation," he said.

He added, "We're seeing language that changes 'free exercise,' which is the Constitution, to 'freedom of religion,' which means you can do what you want within the four walls of your church, but you can't bring it out."