In a petition filed in Seattle federal court, the agency called Starbucks' plan to reorganize the stores into a "Heritage District," and force 73 workers to reapply for their jobs, an illegal response to unionization efforts at one of the stores, at 1st Avenue and Pike Street.

By refusing to rehire 16 of the 22 workers there, Starbucks "chilled employees' support for the union" at the other two stores "by sending a clear message about what would happen if they unionized," the NLRB said.

The petition seeks an injunction to block Starbucks from firing or disciplining workers, denying them higher wages and benefits, or forcing them to reapply for jobs because of their union activities.

It also seeks to require Starbucks to offer jobs, with back pay and benefits, to the 33 people it let go.

Starbucks did not immediately respond to requests for comment.

The company has recently had strained relations with some employees, including last month when workers at dozens of U.S. stores went on strike to protest managers' decisions not to let them hang rainbow flags and other Pride month decor.

Starbucks ended its last fiscal year with 15,873 U.S. stores, of which 9,265 were company-operated and 6,608 were licensed. The company-operated stores employed about 248,000 people.

The case is Hooks v Starbucks Corp, U.S. District Court, Western District of Washington, No. 23-01000.