A diverse coalition of faith-based groups is urging politicians to avoid appealing to voters based on religious lines – a practice they say is "divisive" and contrary to American ideals.

"There is a point…where an emphasis on religion in a political campaign becomes inappropriate and even unsettling in a religiously diverse society such as ours," writes the group, which includes Christian, Islamic, Jewish, Hindu and Sikh organizations. "Appealing to voters along religious lines is divisive. It is contrary to the American ideal of including all Americans in the political process, regardless of whether they are members of large and powerful religious groups, religious minorities, or subscribe to no faith tradition."

They continue: "Voters should be encouraged to make their decisions based upon their assessment of the qualifications, integrity, and political positions of candidates. A candidate's religious beliefs – or lack thereof – should never be used by voters, nor suggested by political candidates, as a test for public office or as a shorthand summary of a candidate's qualifications."

The issue of religion has come to the forefront of the political debate in recent weeks, mostly fueled by the rising prominence of GOP presidential candidate Rick Santorum, a former Pennsylvania senator who has championed his Christian faith throughout his campaign and used biblical language and examples in discussing public policy.

Santorum came under fire last weekend after criticizing President Obama for basing his policies on a "phony theology" and saying that the president is "trumping the values of the church."

Santorum later clarified that he was speaking of the president's "worldview" and "ideology" and that he doesn't question Mr. Obama's faith.

On Tuesday, former Massachusetts Governor Mitt Romney also took a religious stab at the White House, saying that Obama has "fought against religion" and that it is seeking to implement a "secular agenda" into the nation's policies.

"Unfortunately, possibly because of the people the president hangs around with, and their agenda, their secular agenda - they have fought against religion," Romney said at a town hall meeting in his home state of Michigan.

The Obama campaign responded by calling Romney's comments "disgraceful" and "misleading."

"These ugly and misleading attacks have no place in the campaign and they provide a very clear contrast with what President Obama is talking about: how to restore economic security for the middle class and create jobs," said Lis Smith, an Obama campaign spokeswoman.

The Rev. C. Welton Gaddy, president of the Interfaith Alliance and one of the signers on the coalition's letter, said that he has been "deeply disturbed by the disproportionate role religion has played during recent election cycles with some candidates seeming to be running for 'pastor-in-chief' rather than 'commander-in-chief.'"

"Candidates are free to speak about their faith – if it's important to them – as a way of giving voters insight on who they are, but a line is crossed when a candidate implies that they should receive your vote because of their faith," Gaddy said. "Religion is not a political football to be used by candidates for tactical advantage, instead It should be a force that brings diverse people together with mutual respect and understanding."

J. Brent Walker, executive director of the Baptist Joint Committee for Religious Liberty, said that, "Candidates do not have to check their religion at the door of the offices they seek. But they need to understand that they serve people of other faiths and of no faith. Resorting to religious language that sets people of faith against each other harms political discourse and sows religious discord."

Meanwhile, faith and politics remained in the spotlight this week as evangelical leader Franklin Graham gave his opinion on the faith some of the GOP hopefuls and President Obama.

In a Tuesday interview on MSNBC's Morning Joe, Graham, the CEO and president of the Billy Graham Evangelistic Association, said he firmly believes that Rick Santorum and Newt Gingrich are Christians but he's not so sure about the president.

"You have to ask [Mr. Obama]. I cannot answer that question for anybody," Graham told MSNBC's Morning Joe on Tuesday. "All I know is that I'm a sinner and that God has forgiven me of my sins because I put my faith and trust in Jesus Christ, that's all I know."

But when asked if he thinks Rick Santorum is a Christian, Graham answered promptly, "I think so…because his values are so clear on moral issues, no question about it. And I just appreciate the moral stand that he takes on these things." Graham also said that he thinks Newt Gingrich is a Christian based on the candidate's word.

On former Massachusetts Governor Mitt Romney, Graham says that he "likes him," but made it clear that he doesn't see the GOP candidate as a Christian.

"He's a Mormon…most Christians would not recognize Mormonism as part of the Christian faith," he said.

Graham further noted that he couldn't deny that the president is "categorically" a Muslim because "Islam has gotten a free pass under Obama."

"Under President Obama, the Muslims of the world - he seems more concerned about them than the Christians being murdered in the Muslim countries," said Graham.

President Obama has publicly declared his Christian faith on numerous occasions, most recently at the National Prayer Breakfast earlier this month, where the president spoke of "loving thy neighbor as thyself" and Jesus' teaching that "for unto whom much is given, much shall be required" as important values, especially for the economy.

The president also made special note of his meeting in 2010 with the Rev. Billy Graham, Franklin Graham's father, calling it one of the "great honors" of his life.

He recounted in detail that after the 93-year-old preacher had prayed for him that he felt the "Holy" Spirit" leading him to pray for Graham.

"And the fact that I would ever be on top of a mountain, saying a prayer for Billy Graham -- a man whose faith had changed the world and that had sustained him through triumphs and tragedies, and movements and milestones -- that simple fact humbled me to my core," Obama said.

"I have fallen on my knees with great regularity since that moment -- asking God for guidance not just in my personal life and my Christian walk, but in the life of this nation and in the values that hold us together and keep us strong," he continued. "I know that He will guide us. He always has, and He always will."