NASHVILLE, Tenn. (AP) — Volkswagen on Monday announced plans to appeal a National Labor Relations Board ruling that upheld a unionization vote among a portion of workers at the German automaker's lone U.S. assembly plant in Tennessee.

The United Auto Workers union criticized the move as a "stall tactic that won't work," and called on the federal labor panel to issue an unfair labor practice complaint against Volkswagen.

"At a time when Volkswagen already has run afoul of the federal and state governments in the emissions-cheating scandal, we're disappointed that the company now is choosing to thumb its nose at the federal government over U.S. labor law," said Gary Casteel, the UAW's secretary-treasurer.

The workers specializing in the maintenance of machinery and robots at the Chattanooga factory in December voted 108-44 in favor of UAW representation, ending the union's decades-long losing streak among foreign automakers in the South.

Volkswagen Chattanooga spokesman Scott Wilson said that the company is seeking an appeal in federal court because the National Labor Relations Board "declined to fully evaluate" its argument that labor decisions should only be made by the entire hourly workforce of about 1,400 employees.

"Volkswagen respects the right of all of our employees to decide the question of union representation," Wilson said in an email. "This is why we disagree with the decision to separate Volkswagen maintenance and production workers and will continue our effort to allow everyone to vote as one group on the matter of union representation."

The decision comes amid Volkswagen's ongoing efforts to cope with the fallout from its diesel emissions cheating scandal that the company said would cost it $18 billion for 2015 alone. A federal judge on Thursday said VW had agreed with the government to buy back as many as 482,000 diesel cars, as well as pay to make up for the cars' pollution.

The NRLB earlier this month in a 2-1 ruling found that Volkswagen's challenge of the union vote raised "no substantial issues warranting review." The skilled-trades workers "share a community of interest" in terms of qualifications, training, supervision and hours that are distinct from production workers in the assembly, body weld and paint shops.

The decision draws on a landmark 2011 NLRB decision in favor of certified nursing assistants at Specialty Healthcare and Rehabilitation Center of Mobile, Alabama, that paved the way for the formation of more of what labor opponents deride as "micro units."

In that case, the nurses sought to create a 53-person bargaining unit represented by the United Steelworkers at the exclusion of other workers at the nursing home. The NLRB ruling in favor of the nurses was upheld in 2013 by the 6th Circuit Court of Appeals, which also has Tennessee in its jurisdiction.

Volkswagen Group of America, which is based in Herndon, Virginia, hasn't said where it will file its appeal.

Richard Hurd. a labor relations professor at Cornell University, said Volkswagen's hardball tactics on the UAW vote come as a surprise because of the strong union role on the company board in Germany, where worker representatives control half the seats.

"The union in Germany does not want the company in the United States to take a hostile position toward the UAW," Hurd said. "Maybe this is just Volkswagen trying to keep conservative politicians in the South happy."

Republican politicians in Tennessee and across the region have long spoken out against the United Auto Workers gaining a foothold among foreign owned plants. And before a 2014 union vote at the plant, Republicans in the state Legislature warned that state grants and incentives could be lost if the UAW won.

The union blamed its 712-626 defeat on unfounded fears sown by labor opponents before the election.