Houses of worship should obey federal tax law and stay out of partisan politics, Americans United for Separation of Church and State has advised religious leaders in a national mass mailing.

Americans United has sent over 60,000 letters to clergy across the country to remind them that federal law prohibits tax-exempt entities, such as houses of worship, from endorsing candidates for public office.

“People don’t join churches because they want to be told how to vote,” said the Rev. Barry W. Lynn, executive director of Americans United. “Our letter reminds religious leaders about what the law requires, why it makes sense and how it could affect them.”

AU sent letters to a wide range of Christian denominations as well as synagogues and mosques.

Said Lynn, “Most clergy of all faiths know it’s inappropriate to use their pulpits to stump for political candidates. But there are very vocal misguided religious and political forces that constantly prod religious leaders to violate federal tax law. We urge clergy to just say no.”

The mass mailing comes as Religious Right groups are stepping up their efforts to persuade pastors to politicize their pulpits. This weekend, the Family Research Council (FRC) is holding its annual “Values Voter Summit” in Washington, D.C., an event that is essentially a religion-based rally for Republican candidates.

The FRC and the American Family Association have also sponsored an “iPledge Sunday” project to encourage hundreds of evangelical churches to get involved in the election.

Next month, the Alliance Defending Freedom, a Religious Right legal group founded by TV and radio preachers, is urging conservative Christian pastors to violate tax law by endorsing or opposing candidates from the pulpit on the so-called “Pulpit Freedom Sunday” Oct 7.

With so much going on, Americans United says, some clergy may be confused about what tax-exempt houses of worship can and can’t do. To help clear the air, Americans United is sending out thousands of informational letters and making various resources about church politicking available through a website called projectfairplay.org.

Several recent polls, Lynn noted, have shown a majority of Americans oppose pulpit politicking. Americans of all political persuasions and faith backgrounds are increasingly saying they want their houses of worship to unite people, not divide them by introducing partisan politics.

“Church-based electioneering divides congregations and communities, violates federal tax law and diverts attention from the true mission of religious communities,” Lynn said. “It’s simply not good for anyone.”

Americans United for Separation of Church and State today asked the Internal Revenue Service to investigate a New York City church that endorsed Republican presidential candidate Mitt Romney in its church bulletin.

The Church of Saint Catherine of Siena’s Sept. 2 bulletin contains a column by the Rev. John Farren, a member of the congregation’s pastoral staff. Titled “From Father Farren, O.P.,” the essay reprints an appeal by several former U.S. ambassadors to the Vatican calling on Catholics to vote for Romney.

The appeal, which Farren reproduced in full, criticizes the Obama administration and concludes, “We urge our fellow Catholics, and indeed all people of good will, to join with us in this full-hearted effort to elect Governor Mitt Romney as the next President of the United States.”

In a complaint to the IRS sent today, the Rev. Barry W. Lynn, executive director of Americans United, requested an investigation. Lynn noted that federal law forbids non-profit churches from intervening in elections. He also pointed out that IRS rules specifically state that tax-exempt entities may not reprint endorsements made by other groups and people.

“This is an audacious attempt by a tax-exempt church to intervene in the presidential election,” Lynn said. “This is a church, not a political action committee. It should play by the reasonable rules that other tax-exempt organizations follow.”

Americans United’s Project Fair Play encourages religious organizations to learn about the provisions of federal tax law. When churches or other religious groups flagrantly violate the law, AU files complaints with the IRS.