Two-thirds of Americans believe that Christians face increasing intolerance in the US, a new survey has found.

LifeWay Research on Wednesday released its findings that six in 10 Americans say religious liberty is on the decline – up from just over half (54 per cent) in 2013.

However, a growing number also believe that American Christians complain too much about how they are treated; rising from 34 per cent in 2013 to 43 per cent in 2015.

"More Americans worry the US has a hostile environment for religious liberty," said Ed Stetzer, executive director of LifeWay Research. "As this perception grows, some approve of it while others speak up against it."

The survey also found that evangelical Christians (71 per cent) and regular churchgoers (70 per cent) are most likely to agree that religious freedom is declining in the US.

Catholics and non-evangelicals, meanwhile, are less convinced, with 56 per cent and 55 per cent agreeing with the sentiment respectively.

Of those who identified as having no religious faith, 46 per cent said religious liberty was declining. Almost half (48 per cent) agreed that intolerance toward Christians has increased, a figure that rose to 82 per cent of evangelicals and 74 per cent of Protestants.

Stetzer said: "Christians are particularly sensitive to what they see as intolerance towards their faith, but they share a common concern with people of other faiths – that religious liberty in general is declining. And this perception is growing rapidly."

However, many Americans still believe that Christians excessively protest their treatment. More than half of those with no faith (59 per cent) and 53 per cent of those who rarely or never attend worship said complaints by Christians are disproportionate.

This view isn't limited to non-Christians, however. More than a third of Christians (38 per cent) agree.

"Most people now believe Christians are facing intolerance, however, a surprisingly large minority perceives Christians to be complainers," Stetzer said. "Both of those facts will matter as Christians profess and contend for their beliefs without sounding false alarms around faux controversies. It won't be easy to strike that balance."