The Freedom From Religion Foundation (FFRF) has written a letter to President-elect Donald Trump asking him to remove any references to religion from the inauguration ceremony on Jan. 20.
In the letter, the Wisconsin-based organization urged Trump to refrain from using the phrase "so help me God" when he takes the oath of office, arguing that it was not included in the exact wording of the presidential oath.
"In its altered, religious form, the oath has become a symbol of the disregard many in our nation have shown for our secular constitutional principles. Reciting the presidential oath in its original form would be an important symbolic step toward divorcing American politics from religion," the group stated.
It claimed that the George Washington and some of the presidents that came after him did not use the phrase when they took their oath.
The FFRF also suggested that Trump should place his hand on the U.S. Constitution instead of the Bible during the ceremony.
The group noted that Trump has invited several faith leaders, such as Franklin Graham, Cardinal Timothy Dolan, Rabbi Marvin Hier and Pastor Paula White to pray at the event. It contended that prayers should not be a part of the inauguration ceremony.
"If you wished to hold a private religious convocation to personally celebrate your inauguration with religion, of course we would have no objection based on the Establishment Clause. But we and our membership do most strenuously object to turning a secular event into a religious circus," the FFRF wrote.
The organization made a similar request for Barack Obama's second inauguration ceremony, but it was ignored.
Meanwhile, several groups have planned to stage protests on inauguration day. The National Park Service has received more than 30 permit applications but only three were approved.
The ANSWER Coalition, the American Constitution Society and the Black is Back Coalition, was allowed to hold events near the parade route, but only ANSWER was granted a permit on inauguration day. A pro-marijuana legalization group is planning to distribute 4,200 joints at the inaugural site.
Up to 900,000 are expected to attend the ceremony on Jan. 20. The Women's March is anticipated to be the largest demonstration in Washington on Jan. 21.