Religious leaders will be excluded from the 10th anniversary memorial service of New York City's 9/11 tragedy.

Critics of the decision argue that religious leaders played an important role during and after the tragedy and should be included.

Former New York Deputy Mayor Rudy Washington, who was serving in office at the time of the September 11, 2001 attack, expressed outrage at the exclusion in an interview with The Wall Street Journal.

“This is America, and to have a memorial service where there's no prayer, this appears to be insanity to me. I feel like America has lost its way,” Washington said.

A spokesperson for New York's City Hall told The Wall Street Journal that previous 9/11 anniversary memorials did not include religious leaders and they wanted to strike a similar tone with the 10th anniversary.

“There are hundreds of important people that have offered to participate over the last nine years, but the focus remains on the families of the thousands who died on September 11,” the spokesperson said.

City Council Member Fernando Cabrera, a pastor at New Life Outreach International, told The Wall Street Journal that religious leaders were “one of the pillars that carried us through".

"They were the spiritual and emotional backbone, and when you have a situation where people are trying to find meaning, where something is bigger than them, when you have a crisis of this level, they often look to the clergy.”

John Long, director of the Federation of Fire Chaplains for the Mid-Atlantic, seemed confused when he heard that religious groups would be excluded from the 10th anniversary 9/11 memorial service.

In an interview with The Christian Post, Long said, “You can't have a memorial service without religion. If it wasn't for God and his direction, you couldn't have memorial services to begin with.”

Rabbi Joseph Potasnik, executive vice president of the New York Board of Rabbis, told The Wall Street Journal that he sympathised with city officials because one of the difficulties would be finding people to represent the diversity of religious groups in New York.

“Who's going to agree as to who the representatives of the faith … will be? We have all the different groupings. If we have four denominations, what about the fifth denomination? There are practical considerations when planning something, where you want to be as inclusive as possible but sometimes you find it impossible to have everyone present who should be present. It's very difficult,” Potasnik said.

Long said he does not buy that argument. “For the National Day of Prayer they include different religious groups,” Long explained. “What's the difference between the National Day of Prayer and the 10th anniversary memorial?”

There have been other controversies involving religion and ground zero, the site of the 9/11 attacks on the World Trade Centre.

Last summer, there was a controversy about the construction of an Islamic community center a few blocks from ground zero, dubbed the “ground zero mosque”. Critics claimed that the group building the center had ties to radical Islamic groups and that it would desecrate the “sacred ground” of the 9/11 attack site.

Supporters argued that the builders are peaceful and one of the goals of the center was to build better relations between Muslims and other religious groups. Supporters also pointed out that the “ground zero mosque” would be neither a mosque nor at ground zero.

In a separate controversy, an atheist organization, called American Atheists, filed a lawsuit over the inclusion of the “9/11 cross” in the 9/11 memorial and museum. The cross is two steel beams forming a small letter “t”, or cross, that was found in the World Trade Center rubble after the 9/11 attacks.

American Atheists argue that the 9/11 cross on public property violated the Establishment Clause of the First Amendment because it is state-sponsored religion. Supporters of the 9/11 cross argue that the cross was a meaningful symbol to many New Yorkers in the aftermath of the attack, and thus, appropriate to include in a memorial and museum devoted to remembering the events of September 11, 2001.

New York Mayor Michael Bloomberg has defended both the Islamic community center and the 9/11 cross.