CHATTANOOGA (AP) — Attorneys for Volkswagen's lone U.S. factory in Tennessee on Tuesday argued against efforts by maintenance workers, who make up 12 percent of blue-collar workers at the plant, to seek a union election.

The workers, classified by Volkswagen as "skilled trades" employees, make up about 160 out of 1,400 hourly positions at the Chattanooga assembly plant. They have petitioned the National Labor Relations Board to schedule a vote for them to be represented by the United Auto Workers for the purposes of collective bargaining with the German automaker.

But during a board hearing at the federal courthouse in Chattanooga, Volkswagen argued that the maintenance workers' role at the plant is not sufficiently distinct from the remaining hourly employees to justify the creation of their own collective bargaining unit.

The UAW's attorney, Michael Schoenfeld, disagreed, noting that the maintenance employees have enhanced electrical and mechanical skills and training requirements; work different schedules; and even wear different uniforms than their colleagues in assembly, body welding or the paint shop.

In an election involving all eligible hourly workers at the plant last year, workers voted 712-626 against UAW representation following heavy campaigning by anti-labor politicians and groups.

After losing that vote, the UAW formed Local 42 in Chattanooga to work toward representing all blue-collar workers at the plant. The chapter is certified under a special labor policy VW created at the plant that does not include collective-bargaining rights.

Volkswagen wants to avoid joining a trend of "micro units" gaining collective bargaining rights for small groups of workers following a landmark 2011 labor relations board decision in favor of certified nursing assistants at Specialty Healthcare and Rehabilitation Center of Mobile, Alabama.

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 board's ruling, which was upheld by the 6th Circuit Court of Appeals, requires employers seeking to prevent the creation of smaller bargaining units to show that the excluded workers share an "overwhelming community of interest" with the smaller group.

"We're not here to re-litigate Specialty Healthcare, but we think it was wrongly decided," said Volkswagen attorney Arthur Carter.

Carter argued that the maintenance and production workers have much in common, including health and retirement benefits; pay schedules and bonuses; and the plant's labor policy under which both are represented by the UAW.

The labor relations board has drawn the ire of Republicans and national business groups such as the U.S. Chamber of Commerce for another micro-unit decision last year in in favor of fragrance and cosmetics salespeople at a Macy's store in Saugus, Massachusetts.

Macy's argued unsuccessfully that at minimum, the entire 120-person sales staff at the store should be eligible to decide on collective bargaining rights through the United Food and Commercial Workers Union, rather than just the 41 people working in the cosmetics and fragrances department.

But the board voted 3-1 that "the cosmetics and fragrances employees are a readily identifiable group who share a community of interest among themselves," making them eligible to become their own bargaining unit.

The 5th Circuit Court of Appeals last month heard oral arguments in Macy's challenge of the decision, but has yet to issue a ruling.

U.S. Sen. Lamar Alexander is among several lawmakers supporting federal legislation to reverse the board's decisions on Macy's and Specialty Healthcare. In a Senate floor speech last year, the Tennessee Republican decried those rulings as laying the groundwork for a flood of tiny bargaining units.

"Imagine if every department of Macy's decided to form a union," he said. "The employer would have dozens of different groups to negotiate with, and the different unions would be fighting each other over who got the better raises and break rooms in terms of employment."

At Tuesday's hearing over the Volkswagen plant, assembly shop general manager Chad Butts said he worried about creating a division between maintenance and production workers over wage if a separate collective bargaining unit were created.

"There are countless times they work together" on the factory floor, Butts said. "You don't have to go find a maintenance team member. They're out there."