A group advocating separation of church and state has filed a complaint with the Internal Revenue Service against six churches it says flagrantly violated federal laws that prohibit clergy members from endorsing political candidates.

The six churches were participants in the so-called Pulpit Freedom Sunday, organized and promoted by the Alliance Defense Fund, a nonprofit legal support group intent on challenging the federal ban on political endorsements by clergy members.

The alliance has promised to provide legal support for the churches that face legal action.

In all, ADF says 31 churches participated in the sermon challenge, and two more are planning to do so soon. The alliance argues that the federal rules violate the First Amendment right to free speech.

“Pastors have a right to speak about Biblical truths from the pulpit without fear of punishment. No one should be able to use the government to intimidate pastors into giving up their constitutional rights,” said Erik Stanley, senior legal counsel for the organization, in a press release.

Opponents argue that the issue is not about free speech, but over the use of tax-exempt dollars to promote a partisan political agenda.

“When five of the six pastors choose to endorse John McCain, it’s hard not to see the ADF scheme as partisan in character,” said Barry W. Lynn, executive director of Americans United for Separation of Church and State, in a written statement.