US Presidential hopeful Hilary Clinton gave an unusual insight into her faith as she spoke to voters in the crucial state of Iowa on Monday.

In a small school in Knoxville, the former Secretary of State told how Christianity had influenced her life and criticised politicians who used Christianity as a tool to "condemn" and "judge", according to Time.

""I am a person of faith. I am a Christian. I am Methodist," Clinton said in response to an audience question.

"My study of the Bible and my many conversations with people of faith has led me to believe that the most important commandment is to love the Lord with all your might, and to love your neighbour as yourself. That is what I think we are commanded by Christ to do," she said.

More than three-quarters of voters in the key Primary state of Iowa consider themselves Christians. Nearly one-third say they are evangelicals who tend to swing towards Republican candidates.

"I have been very disappointed and sorry that Christianity, which has such great love at its core is sometimes used to condemn so quickly and judge so harshly," she said in a clear dig at Republican candidates' opposition to Syrian refugees.

"There is so much more in the Bible about taking care of the poor, visiting the prisoner, taking in the stranger, creating opportunities for others to be lifted up."

Clinton, who grew up in a Methodist household, told the audience her mother taught her about Christianity.

"I am by no means a perfect person," she added.

"I will confess that to one and all. But I feel the continuing urge to try to be better, to try to be more loving even with people who are quite harsh."

"I am in awe of people who can truly turn the cheek every time," Clinton said.

"Who can go the extra mile that we are called to go. Who keep finding ways to forgive and move on. Those are really hard things for human beings to do."

Jessica Manning, a 36-year-old high school counsellor who asked the question said she was convinced by Clinton's answer.

"I didn't know how strongly she felt about speaking about her Christianity. Some of the Republicans are using it to gain votes but she doesn't do that a lot."