A Washington anti-union group filed complaints with the National Labor Relations Board on behalf of eight workers who allege they were misled by UAW officials attempting to organize Volkswagen Chattanooga assembly plant.

The National Right to Work Foundation filed the complaints at the NLRB’s Atlanta office.

The filing shows the mounting tension around an organizing push by the UAW, which is in talks with VW executives about setting up a German-style labor board at the plant.

The union says a majority of the plant’s 2,700 workers have signed union cards expressing interest in the UAW, one of the first steps necessary to establish a collective bargaining unit.

The eight workers say they were told that signing a card was a sign of support for a secret-ballot election, not support for the UAW. They also contend union officials told workers who asked to revoke their signed cards that they would need to visit the union’s local organizing office to do so.

“This case underscores how card check unionization schemes make it ‘easy to check in, but impossible to check out,'” Mark Mix, president of the foundation, said in a statement.

The UAW countered that the complaints are a “frivolous and baseless” attempt to delay negotiations between the union and Volkswagen, Reuters reported.

The UAW said it has also made clear that the cards can be revoked.

Chip Harrell, the regional director at the NLRB office in Atlanta, confirmed the charges were filed today.

Representing the plant’s workers would be a major victory for the UAW, which has struggled to organize foreign-owned assembly plants in the South and offset a steady decline in its membership ranks.

UAW President Bob King wants VW to recognize the union as its bargaining partner based on the cards — a step that Tennessee politicians and business leaders are urging VW not to take.

Anti-union activists like the National Right to Work Foundation hope the NLRB filing will force the UAW to back away from a card check, or at least put pressure on VW to insist upon a secret-ballot election.

The UAW says it would like to avoid a secret-ballot election.

During an election, union opponents often barrage workers with anti-union messages in person and over the airwaves, and union support often wanes.

“We are not seeking a vote necessarily; we want some way to get fair recognition,” Gary Casteel, the head of the UAW’s Tennessee-based Region 8, told the Tennessean newspaper this month. “We know if we go for a traditional election where the outside organizations could campaign against us, we’d probably lose.”

A successful organizing drive at the Chattanooga plant, which has built the Passat sedan since it opened in 2011, could make it easier for the UAW to win support at other plants it has targeted, such as Nissan Motor Co.’s assembly plant in Canton, Miss., and a Mercedes-Benz assembly plant in Vance, Ala.

VW has not decided how to handle the UAW organizing effort, but the company’s goal is to offer workers a “works council” that would give them a say in how the Chattanooga plant is run. VW’s other assembly plants have such a council.

In an interview this month with Automotive News, Horst Neumann, the board member for human resources at VW, said company lawyers are working on a proposal and may have something to discuss by the Detroit auto show, which starts Jan. 14.

“As I’m learning, you can do a lot within the [American] legal framework,” he said Sept. 9. “It’s an open country, the United States.”