The nation’s largest Muslim advocacy organization has been hit with charges of union busting amid a row with a labor union attempting to organize its Washington, D.C., staff.

The Maryland-based Service Employees International Union Local 500 filed a charge of unfair labor practices against the Council on American-Islamic Relations -- alleging that the Islamic civil rights group denied union organizers access to the workplace, made threatening and coercive statements to workers ahead of a planned organizing vote and fired at least three employees for attempting to organize workers.

The charges -- which delayed the scheduled Monday workplace organizing vote by CAIR’s staff scheduled -- were filed with the National Labor Relations Board, the United States main federal labor law enforcement agency. The filings were posted on the NLRB’s website, but the actual complaint from the SEIU Local 500 has not been made public.

A spokesman for SEIU Local 500 told Fox News that the filing and the delay of the vote on Monday was necessary because of the atmosphere of “intimidation and fear” at CAIR.

“The vote was postponed because there is so much union busting going on over there that it is impossible to have a fair election,” said SEIU Local 500 spokesman Christopher Honey. “The whole things seems totally antithetical to what they do with their work at CAIR.”

In a statement provided to Fox News, CAIR called the charges leveled against the organization “meritless” and said it “strongly supports the organized labor movement.” The communications director at CAIR, Ibrahim Hooper, did not answer Fox News’ question of whether or not the organization supported its own workers unionizing and instead referred back to CAIR’s statement.

“CAIR has remained neutral throughout this process and respects the free choice of employees,” the statement said. “We look forward to the election going forward as soon as possible.”

CAIR was formed in 1994 under the auspices of working to promote social, legal and political activism among Muslims in America. Over the years the group has had to fend off numerous charges that it is pursuing an Islamist agenda.

While SEIU Local 500 asserts that they filed charges and delayed the vote because of intimidation tactics on the part of CAIR management, Hooper implied that the union wanted a delay because they didn’t have enough votes to actually unionize. If successful, SEIU Local 500 would represent between 17 and 20 non-management employees at CAIR’s Washington D.C. office.

“The vote was not stopped by any action on our part,” Hooper said. “There is only one reason I believe the union would want to delay the vote.”

Workplace rights are #civilrights - which makes @CAIRNational #hypocrites for policy of stopping employees from being able to vote for union — SEIU Local 500 (@SEIULocal500) April 18, 2017

SEIU Local 500 attests that last October they begin the push to unionize after being approached by CAIR employees who told the union they had a majority of employees in support of going that route.

“We went in with the majority of cards on our side,” Honey said.

CAIR has argued to the NLRB that it is a religious organization and exempt from the National Labor Relations Act. But earlier this month, a regional administrator at the NLRD disagreed when ruling that CAIR was "more akin to a secular civil rights group" and therefore its workers were free to unionize – a ruling that CAIR has so far rejected.

“Our allies and supporters should know that this situation has little to do with organizing and employee choice, which we support, and everything to do with the method by which it happens, as well as with protecting CAIR's legal identity as an American Muslim civil rights organization,” the group said in a statement.