The United Auto Workers has failed in its effort to unionize workers at two Mercedes-Benz plants in Tuscaloosa, Alabama, in a blow to the union’s plans to build its membership in the southern states.

The loss on Friday comes amid the UAW’s ambitious union-organizing campaign to organize 150,000 non-union auto workers around the US.

In April the UAW won a landslide victory at the Volkswagen plant in Chattanooga, Tennessee, where 73% of workers voted to unionize.

The final vote was 2,642 against union representation and 2,045 for. Fifty-six per cent of workers voted no.

Southern states have for decades successfully fought off unionization drives in an attempt to keep down labor costs – a practice critics have called the “Alabama discount”.

“Mercedes is a better place thanks to this campaign,” said Shawn Fain in a press conference after the results were announced. He cited the end of two-tier wages and a replacement of the chief executive as some of the successes workers won during the organizing campaign.

He said: “The federal government and the German government are currently investigating Mercedes for the intimidation and harassment that they inflicted on their own workers, and we intend to follow that process.”

At Mercedes, the union faced significantly more aggressive opposition to worker organizing efforts than at Volkswagen, including from Republican elected officials and business groups that campaigned against the union vote.

David Johnston, a worker at the Mercedes battery plant since August 2022, said he jumped at the chance to work at Mercedes when he heard they were directly hiring.

But promises and claims that were made to him when he was hired became exposed as false or misleading, he said, such as workers never being forced to work Sundays, or the two-tier wage system, and unilateral changes made by the company.

“They have changed their own handbook many times since I was originally hired, in just two years. They have also changed our schedules. My schedule personally has changed about six times since I was hired on,” said Johnston.

These factors and his previous experience working under a union contract inspired him to support the unionization effort, he said. Johnston said Mercedes-Benz’s attempt to dissuade workers from unionizing had only assisted workers’ organizing efforts.

Mercedes-Benz moved to head off the union drive by eliminating a two-tier wage system at the plants. That decision came after it was announced 30% of workers had signed union authorization cards.

“That quite honestly backfired for the company. It really showed workers that they’ve been listening to us the whole time, but did not care about us,” said Johnston. “It wasn’t until we decided that we wanted to union that the company even would respond to us.

“This isn’t political, regardless of what the governor wants to say. This isn’t something that the UAW came down to us seeking us to join them. This was us going to them asking them to represent us, that we would be allowed to call the shots on how we organized, and this has been 100% worker-driven. The people that are going to unionize are the people that live in the south.”

Now workers will push for a first union contract at Volkswagen as the UAW sets its sights on expanding their union wins in the auto industry. The UAW has so far announced reaching 30% thresholds of workers signing union authorization cards at a Toyota engine plant in Troy, Missouri, in March and at the Hyundai plant in Montgomery, Alabama, in February.

Sharon Block, a law professor at Harvard Law School and former NLRB official, said: “There are legal avenues open to the UAW to challenge the outcome.

“As Mercedes’ anti-union campaign ramped up, the UAW filed a number of unfair labor practice charges with the NLRB, alleging that Mercedes crossed the line from strongarm to unlawful tactics in the plants. In addition, there is an investigation under way into whether Mercedes violated German law by undertaking such an aggressive anti-union campaign in the US.”

A spokesperson for Mercedes-Benz said: “We look forward to continuing to work directly with our team members to ensure MBUSI is not only their employer of choice, but a place they would recommend to friends and family.”