A non-profit civil rights organisation has asked the US Marines to remove a billboard that says "God bless the military, their families and the civilians who work with them" inside the Marine base in Hawaii.

The Military Religious Freedom Foundation (MRFF), which aims at "ensuring that all members of the United States Armed Forces fully receive the constitutional guarantee of religious freedom," sent an email to Col. Sean Killeen, commanding officer of the Marine Corps Base Hawaii (MCBH), noting that "a sign invoking God's blessings has been erected, and currently stands, on prominent display at MCB Hawaii," according to the Christian News Network.

Blake Page of the MRFF charged that the sign "is a brazen violation of the No Establishment clause of the Constitution, as it sends the clear message that your installation gives preference to those who hold religious beliefs over those who do not, and those who prefer a monotheistic, intervening god over other deities or theologies."

"We recognise the value that religious activity brings to the lives of many. However, this sign is not in keeping with the time, place, and manner restrictions required by law for any military commander to bolster religious principles through the official authority given to their rank and position," he said. "It is our recommendation that this sign be moved to a more appropriate location, such as chapel grounds, or be removed from the installation altogether."

In response, Capt. Timothy Irish told the Marine Corps Times that the issue is being reviewed.

"[Colonel Killeen] has tasked his staff with researching the origin of the sign and its compliance with existing regulations. The Base Inspector's Office is reviewing its files to see if there have been any complaints in the past," Irish said. "MCBH will exercise due diligence to ensure compliance with existing regulations and law, including the Establishment Clause of the US Constitution."

However, retired Chaplain Ron Crews, executive director of the Chaplain Alliance for Religious Liberty, said the MRFF is misinterpreting the Constitution.

"Only someone with a great misunderstanding of the First Amendment or an axe to grind against religion would claim that such a slogan poses a threat or is in any way unconstitutional," he said in a statement issued Friday. "The real threat is posed by those who want to whitewash any reference to God from public discourse—even ones as innocuous and uplifting as this one."

He added, "'God bless our military' is a slogan little different than the official national motto, 'In God we trust,' that appears so publicly on our money, and the courts have repeatedly upheld it. From the founding of our country, every president, including President Obama, has called on God to bless America. We hope that Col. Sean Killeen, the base commander, will stand firm and allow the sign to remain."