A union representing thousands of city workers is suing Philadelphia Mayor Cherelle Parker over her order for them to return to the office.

District Council 47, which represents more than 3,000 municipal workers, sued Ms. Parker on Monday, arguing that the mayor’s order violates state and federal labor law.

The union says that under the National Labor Relations Act, employers must negotiate any changes to unionized workers’ wages or conditions of employment.

According to the union, Ms. Parker has refused to negotiate with the workers since she issued the return to office mandate in May.

“We have worked very hard to build a long standing tradition of negotiating w/past @cityofphiladelphia administrations to build better city government,” the union posted on X. “Why throw that away@phillymayor??? Philadelphians deserve 21st-century city services!”

The union has asked the court to issue a temporary block on any changes to worker conditions that have not been negotiated. The court is expected to hold a hearing on July 11.

The vast majority of Philadelphia’s city workers have already returned to the office full-time, and Ms. Parker says that the return will promote innovation and increase social connectivity.

“It delivers on my promise of an accessible City workforce that is best situated to serve the people of Philadelphia. A more consistent in-office presence will result in work environments where equal employment opportunity and diversity, equity and inclusion are truly realized,” Ms. Parker said in a statement.

• Vaughn Cockayne can be reached at vcockayne@washingtontimes.com.