(CNN) -- In what could prove to be a precedent-setting case, the National Labor Relations Board has issued a complaint against a Connecticut company for firing an employee after she posted critical, derogatory comments about her supervisor on Facebook.
The company, ambulance service American Medical Response, says emergency medical technician Dawnmarie Souza was fired because of "multiple, serious complaints about her behavior," not because she took to a social networking site to describe her supervisor in various unflattering terms, among the mildest of which was comparing the supervisor to a psychiatric patient.
The labor board, a federal agency that oversees union elections and investigates claims of unfair labor practices, accuses the company of illegally terminating Souza and denying her access to union representation during an investigatory review.
The labor relations board argues that workers' criticism of their bosses on social networking sites like Facebook is generally "a protected concerted activity."
"You are permitted to talk about terms and conditions with employees or anyone else, it's public because you are protected under the National Labor Act," says Jonathan Kreisberg, the board's regional director in Hartford, Connecticut.
Kreisberg says that in addition to describing her supervisor in unflattering and sometimes vulgar terms on her Facebook page, Souza also wrote about "how the company allows a 17 to be a supervisor." The 17 reference is the company's jargon for a psychiatric patient, Kreisberg says.
The National Labor Act gives workers the right to form unions and it prohibits employers from taking action against employees -- union or non-union -- for discussing working conditions, says Kreisberg. He adds that the case could be "ground-breaking" because it is in the uncharted legal territory of social networking sites on the internet.
"It was Souza's ... own page; she did this on her own time in her own home. This case is different because in this situation it happened online and the company's rules were unlawfully broad," says Kreisberg.
In a statement to CNN, American Medical Response says it believes that the offensive statements made against the co-worker were not activities protected under federal law.
The company "denies the allegations made by the NLRB and believes the facts will show that they are without merit. The employee in question was discharged based on multiple, serious complaints about her behavior," the statement says.
An attorney representing the ambulance company adds, "This is not about Facebook."
"This employee was terminated after the company received complaints on two separate incidents in 2009. All pointed to Souza's rude and discourteous behavior with patients," says attorney Jackson Lewis.
Souza, who was fired last December and who is seeking reinstatement to her job, declined comment to CNN, saying only that granting an interview would "jeopardize her case at this point."
On the issue of assistance from a union representative, the labor board says Souza wanted help from the union representing the company's workers when she wrote up a response to the company.
The company's lawyer says she was not denied union representation. "Before submitting her response, she checked in with her union representative," says Lewis.
A labor board hearing for the case is scheduled for January 25.