The union representing workers at the historic Blackstone hotel has filed a complaint with the National Labor Relations Board accusing managers of firing at least nine employees for union activity.

The workers are members of Unite Here Local 1, which represents about 15,000 members in the Chicago area.

The union alleges that the Blackstone, a Marriott International, Inc. hotel in the South Loop, refused to bargain with the union in good faith and discriminated against the workers because of their support for the labor group.

Two of the employees participated in the NLRB's investigation of the hotel by giving the labor board sworn statements, according to the complaint.

Unite Here Local 1 President Henry Tamarin, spokeswoman Annemarie Strassel and attorney Eric J. Wiesner did not immediately respond to requests for comment.

Norman R. Buchsbaum, the Blackstone's employment attorney, says there is no merit to the charges. He says the hotel cut staff to cope with a slow economy.

"Under federal labor law, an employer has a right to make entrepreneurial changes to its business," Buchsbaum says. "We have a right to lay off people if there's a lack of work. We have a right to move people from department to department. Whether they're union or nonunion, these are business decisions."

Buchsbaum says the hotel has cooperated with the NLRB during its investigation of previous complaints from the local union, and that it has not fired any workers for supporting the union or giving testimony to the labor board.

According to Unite Here's complaint, filed Monday in the labor board's Chicago office, Blackstone hotel managers shut down the room-service department and fired all of its workers, as well as all workers in the hotel's employee cafeteria. The hotel transferred the work of those departments to other workers, according to the charge.

Buchsbaum says workers transferred to room service and the employee cafeteria are also unionized, and that some are former employees who applied for other jobs.

"Nobody's been terminated because they were part of the union," he says. "We encouraged everybody to apply for new positions."

Further, Buchsbaum says, the hotel is negotiating an employment contract with the local and met with its leadership in January, February, April, May and June. Two bargaining sessions are scheduled for later this month and another for August, he says.

"We think that the government will likely dismiss these charges," Buchsbaum says. "The union ought to better spend its money — and have us better spend our money — trying to work out an agreement rather than running to the labor board every time something happens to the operation of the business."

The hotel and union have not previously agreed on an employment contract, he says.

The Blackstone hotel, part of Marriott's Renaissance group, opened in March 2008, after several years in renovation. Unite Here began representing about 200 workers there in December, but dozens of them tried to part ways with the union earlier this year.

In 1920, U.S. lawmakers gathered at the hotel to choose the compromise Republican nominee Warren G. Harding, who became president. The hotel was named for Timothy B. Blackstone, a railroad executive and the founding president of the Union Stock Yards. His mansion stood on the site.

The 23-floor Blackstone has 328 rooms, four suites and 15 meeting rooms.