Union leaders filed a formal complaint with the National Labor Relations Board Monday, alleging that administrators at Yale-New Haven Hospital violated federal labor laws.

The unfair labor practice charges stemmed from three separate incidents last month in which hospital workers, Yale employees and graduate students were arrested by hospital police while distributing information on unionization outside hospital buildings.

In the complaint, Local 34, the Graduate Employees and Students Organization and the Service Employees International Union District 1199 claimed that Yale-New Haven Hospital “unlawfully threatened and coerced employees” for leafleting.

Hospital spokeswoman Katie Krauss said the charges were without merit and characterized them as “a tactic” designed to advance the unions’ goals.

“My sense is that these charges are part of a broader union effort,” she said.

District 1199, which represents 150 dietary workers at the hospital, has been trying to unionize about 1,800 other hospital workers. The group is closely aligned with Yale’s largest unions, locals 34 and 35, which are involved in their own protracted contract dispute with Yale.

Early last month, Yale-New Haven Hospital police arrested four members of Local 34, Yale’s clerical and technical workers union, who were distributing leaflets outside a hospital building. A week later, two more Local 34 members as well as two GESO members were arrested for distributing information outside the Yale Cancer Center.

All eight were charged with second-degree criminal trespass and face up to a year in jail. The cases are currently set to be settled out of court under community mediation.

Union leaders also criticized Yale officials for not condemning the arrests. Yale leaders said they were not responsible for the arrests because they occurred on hospital grounds. University leaders have long maintained that Yale is separate from the hospital.

Yale spokesman Tom Conroy declined to comment on the charges because they apply to the hospital and not to the University, he said.

Krauss said the workers were arrested because they were blocking entrances. She said she is confident that the hospital’s actions were legal.

“Our desire is not to prevent free speech,” she said. “It’s simply to protect employees, patients, visitors and our property.”

Union spokeswoman Deborah Chernoff said she believed the arrests at the hospital not only violated free speech rights but were also intended to intimidate potential union supporters.

“They had what people refer to as a chilling effect,” Chernoff said. “It makes it seem like communicating about unions is some sort of illicit activity — [leafleting] is one of the few opportunities that people have to learn about the union.”

Union leaders have previously filed unfair labor practice charges against the hospital. Last fall, the union alleged that hospital workers had been harassed while trying to distribute information about an upcoming march. Most charges have been settled between the hospital and the NLRB without hearings, union leaders said.

Krauss said the hospital believes an investigation will show that the charges are unwarranted. She added that these charges, and other ones that the unions have filed against the hospital in recent months, are “a way of generating some attention for their cause.”

The unions filed the charges on the same day that the Public Safety Committee of the New Haven Board of Aldermen unanimously passed a resolution to strip the hospital police of their power to make arrests. At that meeting, two amendments were added to the resolution: one urging the hospital to drop all charges and the other asking Yale President Richard Levin, who sits on the hospital board, to do the same. The resolution will go before the full Board of Aldermen next Monday.