Cast members Lin-Manuel Miranda (left), Christopher Jackson (center) and Phillipa Soo perform a song from the hit musical "Hamilton" for U.S. President Barack Obama and other guests at the White House, March 14, 2016. Reuters

A brewing controversy over labor rights has raised questions about whether the most popular show on Broadway is racist because it actively sought to cast non-white actors. The cast of "Hamilton" has been celebrated by the White House and the Grammys, but a recent casting call aimed at non-white actors may have been illegal, according to media reports Wednesday.

The hip hop musical playing at the at the Richard Rodgers Theater in New York City is looking to expand its cast through open auditions in May as it prepares for a national tour. Critics have complained in the past about the show's use of black and Latino actors to portray the nation's white founding fathers, but the latest debate about "Hamilton" argues its casting violates anti-discrimination laws.

“What if they put an ad out that said, ‘Whites only need apply?’” civil rights attorney Randolph McLaughlin of the Newman Ferrara Law Firm told CBS New York. “Why, African-Americans, Latinos, Asians would be outraged.”

The New York City Human Rights Law prohibits employers from discriminating against a potential hire based on race. “You cannot advertise showing that you have a preference for one racial group over another,” McLaughlin told CBS New York. “As an artistic question — sure, he can cast whomever he wants to cast, but he has to give every actor eligible for the role an opportunity to try.”

A December casting call on Backstage.com for "Hamilton" invited actors of “all ethnicities,” Fusion reported. But a more recent listing asked for "non-white men and women, ages 20s to 30s, for both the Broadway production and upcoming national tours. No theater experience necessary."

New York City's Commission on Human Rights said it has not received any complaints about the production, and producer Jeffrey Seller has defended the casting call. "I stand by it and believe it to be legal," he said.

A spokesperson for the show told CBS the language in the notice was approved by Actors Equity, the Broadway union that requires casting directors “to provide full and fair consideration to actors of all ethnicities.”

But the union's spokeswoman said the language was inconsistent with its policy. “We did not review it before it was posted on the ‘Hamilton’ website,” spokeswoman Maria Somma told the New York Daily News on Wednesday. “If you look at our website, the casting calls all contain the following language: Performers of all ethnic and racial backgrounds are encouraged to attend.”

The multi-ethnic cast of “Hamilton” portrays U.S. leaders such as Alexander Hamilton, Thomas Jefferson, George Washington, James Madison and Aaron Burr. Created by Lin-Manuel Miranda, the show has become so popular that resale tickets go for more than $1,000 a seat and an online lottery saw 50,000 people apply for $10 tickets.