A D.C. streetcar is seen at the eastern end of the line near Oklahoma Avenue and Benning Road in this December 2014 file photo. (Katherine Frey/The Washington Post)

The District’s troubled streetcar program, already facing big questions about its future, has now spawned an ugly labor dispute, with union claims that workers were fired for trying to organize and counterclaims that onboard cameras caught streetcar staff violating safety rules by using cellphones.

The Amalgamated Transit Union Local 689 — which represents Metro workers and was seeking to hold an election this month to unionize private streetcar workers — has filed a complaint with the National Labor Relations Board alleging that the District’s streetcar contractors “conducted a mass termination of a substantial portion of the eligible voters in retaliation for their efforts to organize and be represented by Local 689.”

Federal labor officials have launched an investigation.

District Department of Transportation officials said the fight is between city contractors and the union and that it is up to the labor relations board to resolve the retaliation claim.

But DDOT added in a statement that “RDMT, the streetcar operating company, has a zero-tolerance policy for cell phone use by safety-sensitive employees. Such a policy is consistent with industry standards. . . . Personnel actions taken towards Streetcar operators are made by RDMT in accordance with their safety policies and procedures.”

Jennifer Sweeny, outside counsel for RDMT, said, “we’re confident the NLRB will find no merit to the union’s allegations.” Meredith S. Campbell, attorney for a separate staffing company called The Midtown Group that is working with RDMT, called the union’s complaint “meritless.”

The brawl comes as the entire streetcar program is being reexamined to see whether it is, or can be made, safe enough to eventually open and whether it would make sense financially or otherwise to do so. Three previous mayors have overseen efforts to try to bring streetcars back to the District after more than 50 years, with visions of 37 miles or more of track crisscrossing the city. But the project has faced repeated missteps.

Officials in former mayor Vincent Gray’s administration had scrambled to try to open the ­2.2-mile streetcar line along H Street and Benning Road NE to passengers by the end of last year, but they were blocked by the city’s State Safety Oversight Office. On one icy night last month, a streetcar smacked into two poorly parked cars along H Street then experienced a still-unexplained “flash fire” atop the 35-ton vehicle.

The District’s new transportation chief, Leif Dormsjo, brought in a group of industry experts from the American Public Transportation Association to inspect the system earlier this month. Dormsjo said he is still assessing the APTA “peer-review” team’s initial findings.

“I’m trying to translate some of what the APTA folks gave me, to understand how easy it is to operationalize some of their recommendations,” Dormsjo said.

It is in this environment of uncertainty that organizers sought to bring streetcar workers into the local transit union.

In a statement, the Amalgamated Transit Union’s international president, Larry Hanley, called the streetcar project “misbegotten from the beginning” and added that “streetcar managers failed in almost every aspect of the development of this new system.”

In an interview, Hanley said his union has been working to organize streetcar workers for more than a year and in February reached an agreement with private contractors on the details for holding a vote on whether workers would unionize.

“On the very next day . . . they start firing workers,” Hanley said. “All of a sudden they started to review videos of the workplace, and they claim they saw safety violations in the videos. It’s obvious there’s a connection between the agreement to have an election and their sudden decision to start firing large groups of the workforce.”

Hanley said there is no merit to the claims of safety violations, which he says were simply used as an excuse to block his union. Union officials said seven workers in all were fired after the formal agreement to hold a vote, and two more lost their jobs at earlier points in the organizing campaign. Those fired represent about a third of all streetcar workers, Hanley said.

Campbell, who represents Midtown, which is named along with RDMT in the transit union complaint, said the company disputes the allegations.

“Unions frequently file meritless charges with the NLRB when they fear they will lose an election campaign,” she said in a statement.

“They also file charges when people are unlawfully fired,” responded Dan Smith, assistant general counsel for the Amalgamated Transit Union. Smith added that the fired workers had not previously been disciplined for whatever they’re now accused of doing with their phones, which he said has still not been adequately explained.

“I got to tell ya, to say they have a zero-tolerance policy is pretty fishy. The one thing everyone says is they didn’t do anything different in the last two weeks” with their phones than they had over the previous year, Smith said.