By Dan Merica, CNN

Washington (CNN) - Americans United for the Separation of Church and State has sent a letter to the Internal Revenue Service accusing Pastor Robert Jeffress of violating the law when he posted his endorsement of presidential hopeful Rick Perry on the First Baptist Church of Dallas website.

Jeffress, the head of First Baptist Church, endorsed Perry at Friday's Values Voter Summit, the same event where he called Mormonism a 'cult.' After the event, Jeffress went on a media blitz and posted a video of himself explaining his comments on the church's website.

The Rev. Barry Lynn, executive director of Americans United, said when Jeffress posted the endorsement on the church's website, he was offering an endorsement from the church, a violation of IRS rules for tax-exempt organizations like churches.

"The tax code has a zero tolerance policy when it comes to campaigning for candidates," Lynn said. "If you put something on your church website, it is not enough to put a disclaimer on it."

Michael E. Batts, a CPA who has been practicing in the area of tax exempt organizations for more than 25 years and is not a member of the Dallas church, says the rules are not as black and white, though.

"The mere fact that a church might post video on its website of the comments of its pastor in other settings is not cut and dry," Batts said. "A determination would have to be made as to whether the post represents an endorsement by the church or whether it is something else."

The First Baptist Church put a disclaimer on the videos. "The posting of video clips and media accounts of Dr. Robert Jeffress' recent media appearances does not constitute First Baptist Dallas' endorsement of any political candidate," read the disclaimer.

According to the Americans United letter, "the Internal Revenue Service has never said that disclaimers like this ameliorate candidate endorsements or make them permissible."

The letter also cites a warning on the subject from the IRS. According to an IRS publication on tax exempt organizations, "If an organization posts something on its website that favors or opposes a candidate for public office, the organization will be treated the same as if it... favored or opposed a candidate."

Batts, however, says the actual law is not that specific.

"The law says that a 501(c)(3) tax exempt organization may not endorse or oppose candidates for political office or intervene in political campaigns," Batts said. "The law is not specific as to facts with that level of granularity."

Lynn said this is only the beginning, however, of his organization's filing of complaints with the IRS.

"I would expect there would be (a) geometric increase in the number of complaints," Lynn said. "This whole election is already so awash in religion."

According to Lynn, Americans United expects to file ten times as many complaints as it did in 2008.