PITTSBURGH — The National Labor Relations Board has again accused the University of Pittsburgh Medical Center of engaging in anti-union tactics.

The complaint was announced Thursday by the Service Employees International Union, which has been trying for years to unionize some 3,500 non-clinical employees.

In November, an administrative law judge found UPMC engaged in unfair labor practices and ordered the health network to halt certain practices, including denying non-employee organizers access to its cafeteria, conducting surveillance on employees and organizers, and barring workers from wearing union insignia in non-patient care areas.

UPMC’s appeal of that finding is pending. Meanwhile, the new complaint contains similar allegations, but none more recent than June 2014.

“The SEIU has yet again resorted to manufactured unfair labor practices charges in an attempt to discredit UPMC during its unsuccessful attempt to organize hospital employees,” UPMC said in a statement. “For the SEIU, this is no longer about representing its members but rather about advancing its political goals by creating a media spectacle of protests and unfair labor practice charges that will resurface as long as UPMC hospital employees resist the SEIU organizing activity.”

But Maryanne Williams, who works as a medical coder at University of Pittsburgh Physicians, said the region’s dominant network continues to illegally monitor her union activity and that of other employees.

“UPMC workers and Pittsburgh need our region’s largest employer to make a real commitment to stop violating workers’ rights and let us form our union without illegal harassment or intimidation,” Williams said.