Donald Trump yesterday said "Christians have been silenced like a child" when addressing 700 evangelical pastors and their spouses at the Florida gathering of the American Renewal Project (ARP).

"You have to get the people in your churches to get out and vote," the Republican presidential nominee told the Pastors and Pews conference. "It's not like you represent two per cent of the country. Can you imagine if all your people started calling the local congressman or senator?"

Trump, who has been criticised in Republican circles in recent days for escalating his rhetoric, repeated his accusation that the President and his Democratic rival are the "co-founders" of Islamic State.

"Barack Obama and Hillary Clinton are the founders of ISIS," he said. "These are bad people with bad judgment, we have an incompetent leader."

Trump repeatedly promised to repeal the Johnson amendment which prohibits churches from using their tax-exempt resources to promote political candidates.

The Republican candidate appealed for prayers. "Pray for me. I pray for you," he said. "This will be an election that will go down in the history books. For evangelicals, for Christians, for everybody of religion. This may be the most important election that our country has ever had. So go out and spread the word."

Trump also joked about Heaven, claiming that a successful term in the White House may be his only way to salvation. "And once I get in, I will do my thing that I do very well. And I figure it is probably, maybe the only way I'm going to get to Heaven," he said. "So I better do a good job."

Trump's attempted joke was met with a chuckle but his speech received a standing ovation from the Christian leaders.

A pastor flanked by former Republican presidential candidate Mike Huckabee then led prayers for Trump. "God, we are asking you now for renewed strength and wisdom, and protection over the Trump family and all those who are connected to them," he said.

"I pray, Lord, that you give them clarity and wisdom. I pray, Lord, that you give them a new revelation of the work of the cross and the power of the Resurrection... We ask, Lord, for a manifestation of your presence that is so real, that Lord, he [Trump] will hear from you with clarity and precision, Lord, we know this is a critical juncture for the battle of the soul of this nation. And we believe that the heart of this nation is in your church. May you awaken the hearts of the nation – your church – for a healing of the soul of this nation. God, we ask you to go before the Trumps and be their guard."