FIRST ON FOX: A group of GOP House members sent a letter to Defense Secretary Lloyd Austin on Monday demanding answers about a leaked memo describing what they called "blanket denial of religious accommodation" to the military's COVID-19 vaccine mandate.

Fifteen Republican members of Congress, led by Reps. Jim Banks of Indiana and Darrell Issa of California, were responding to a partially leaked internal memo by the Pentagon's Acting Inspector General Sean O'Donnell to Austin written in June, but circulated on Sept. 2.

The IG writes in the memo that he reviewed "concerning denials of religious liberty accommodation requests from COVID-19 vaccination requirements."

O'Donnell stated that the purpose of the report is "To inform [Secretary Austin] of potential noncompliance with standards for reviewing and documenting the denial of religious accommodation request from Service members." He said that the Department of Defense (DOD) hotline lit up with "dozens" of complaints regarding denied religious exemption requests from military service members.

PENTAGON IN ‘POTENTIAL NONCOMPLIANCE’ WITH LAW AFTER DENYING VACCINE RELIGIOUS ACCOMMODATION REQUESTS: IG

In their letter, the House members cited reports that the Pentagon has overwhelmingly rejected most of the approximately 24,000 service member requests for religious exemptions to the vaccine.

"As of February 2022, the Department of the Navy had granted only a single, partial exemption to its COVID-19 vaccine mandate on religious grounds, and as of July 2022 the Department of the U.S. Army had approved just 20 of over 8,000 requests, the Department of the Air Force had approved less than 130 of over 9,000 requests, and the U.S. Marines had only approved seven of over 3,700 requests," the letter said, adding that at least 75,000 troops face potential discharge because of the vaccine mandate.

NAVY SEALS SEEKING RELIGIOUS EXEMPTIONS TO VACCINE MANDATE FACING INTIMIDATION AND HARASSMENT, SOURCES SAY

Secretary of Defense Lloyd Austin

Secretary of Defense Lloyd Austin testifies before a House subcommittee in Washington, D.C., on May 11, 2022. (AP/Jose Luis Magana)

The members of Congress expressed particular concern that the majority of religious exemptions that DOD did approve were given to service members on the verge of retirement, and that non-religious exemptions were approved "at a far higher rate than religious exemptions."

"This suggests the DOD is applying different policies toward service members' applications based on their religious beliefs and expected employment status," the letter said.

The letter further noted that the IG's report found "denial memorandums we reviewed generally did not reflect an individualized analysis."

California Congressman Darrell Issa

Rep. Darrell Issa speaks during a news conference in El Cajon, California, on Sept. 26, 2019. (AP Photo/Gregory Bull)

"As the memo explains, the described blanket denial of religious accommodation violates DOD Instruction 1300.17, which directs officials to ‘review each [religious accommodation] request individually, considering the full range of facts and circumstances relevant to the specific request,’" the members said, going on to note that such denial would also be in violation of the Supreme Court's ruling in Burwell v. Hobby Lobby.

NAVY QUIETLY ROLLED BACK PUNISHMENTS FOR SEALS SEEKING RELIGIOUS EXEMPTIONS TO THE COVID VACCINE

The members concluded by requesting a complete copy of the IG's June memo; all records of religious accommodation requests regarding COVID-19 vaccinations submitted to the Navy, Air Force and Army; and all Pentagon internal policy directives related to the review process for religious accommodation requests regarding COVID-19 vaccinations.

The members also urged Austin to remind all DOD employees and officials of their legal responsibility to take appropriate measures to preserve all documents, communications and other records in accordance with federal law.

Rep. Jim Banks at the U.S. Capitol

Rep. Jim Banks speaks at a press conference following a Republican caucus meeting at the U.S. Capitol on June 8, 2022. (Kevin Dietsch/Getty Images)

In addition to Banks and Issa, the other members who signed their name to the letter were Reps. Marjorie Taylor Green of Georgia, Lance Gooden of Texas, Doug Lamborn of Colorado, Christopher Smith of New Jersey, Diana Harshbarger of Tennessee, Thomas Massie of Kentucky, Elise Stefanik of New York, Vicky Hartzler of Missouri, Jodey Arrington of Texas, Louie Gohmert of Texas, Glenn Grothman of Wisconsin, Clay Higgins of Louisiana, and Carlos Gimenez of Florida.

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In response to the IG report last week, a Pentagon spokesperson told Fox News Digital in a statement: "The department has a Uniform Standards for Mandated Coronavirus Vaccination Working group that meets regularly to ensure the department is doing everything we can to best protect our service members and their families."

Fox News' Kelly Laco contributed to this report.