Donald Trump is failing to gain support among American church leaders, new research has found, with just five per cent of Republican Protestant pastors saying they would vote for him.

Results of a survey conducted among ministers were released by Lifeway research, where senior church leaders were asked: "If the 2016 presidential election were held today, for whom would you vote?"

Ted Cruz won the race among pastors who identified as Republican, with 29 per cent of those polled saying they would vote for him. More than a third (39 per cent) were undecided, but one in ten said they would vote for Ben Carson, while eight per cent chose Marco Rubio. Just five per cent named Donald Trump as their top choice, which suggests there is a "huge gap between the pulpit and the pew," said Ed Stetzer, Lifeway's executive director.

"One of the few religious groups that national polls track are evangelical Christians, and it is hard not to notice a surprising gap between them and their pastors," he explained.

"Based on most other polls, rank-and-file evangelicals and church attendees are most likely supporting Trump. Yet pastors are undecided or more likely to support Cruz. The absence of support for Trump is similar to unscientific surveys of evangelical leaders from the National Association of Evangelicals and WORLD Magazine that have consistently pointed to Rubio.

"Simply put, it's a bizarre election season," Stetzer added.

Hillary Clinton was by far the most popular choice among pastors who identified as Democrat. She received 38 per cent of the vote, while 31 per cent said they were undecided and 23 per cent said they would vote for Bernie Sanders. Just under one in ten (eight per cent) said they would vote for a different Democrat candidate.

The survey of 1,000 Protestant pastors also found that more than half (54 per cent) labelled themselves Republican, while just one in seven identified as Democrat.

Pastors over the age of 64 are more likely to be undecided than younger church leaders, but are also more likely to favour Trump.

Clinton is less popular among white pastors than she is among those of other ethnicities. Cruz, however, is more popular with white pastors.

Trump's failure to win the favour of Republican church leaders is perhaps not entirely unsurprising as he is not widely regarded as "religious," another recent survey found.

A poll conducted by Pew Research found that "being an atheist remains one of the biggest liabilities that a presidential candidate can have" and "Trump is not widely viewed as a religious person, even by those in his own party."

Only five per cent of Republicans and those who lean toward the Republican Party said Trump is a "very religious."

However, Trump remains the Republican frontrunner. According to NBC News, he pulled ahead of Ted Cruz yesterday with a seven-point lead in the polls, just several days ahead of the Iowa caucus on February 1.