The closely-watched vote came as the US labour movement is fighting for its survival after decades of shrinking membership rolls.
Volkswagen workers voted against joining the union in a final vote of 712 to 626 yesterday.
"While we're outraged by politicians and outside special interest groups interfering with the basic legal right of workers to form a union, we're proud that these workers were brave and stood up to the tremendous pressure from outside," said UAW secretary-treasurer Dennis Williams, who directs the union's transnational program.
The unionisation efforts faced stiff opposition from local politicians, who warned that a UAW victory would make it harder to attract new jobs to Tennessee and even threatened to withhold tax credits that would help VW expand production.
A total of 1,338 employees at VW's Chattanooga plant - 89 per cent of the workers - voted over a three-day period in the secret ballot election, which was monitored and tallied by the National Labour Relations Board.
Volkswagen opened the door to the UAW last year under pressure from German unions to give the Tennessee plant a seat on VW's global works council, which gives employees a say in the management of the company.
Volkswagen's management "seemed neutral to positive" towards the UAW's attempt to organise the workers, said Jack Nerad, executive editorial director at Kelley Blue Book, a vehicle valuation company that also provides analysis of the automotive industry.
And yet the union "still failed to gain certification," Nerad said in a statement, describing it as a "serious setback" for the union.
"The UAW's attempts to organise other non-union plants in the United States are very unlikely to be greeted with as much cooperation from other manufacturers, so this could mark the end to UAW hopes to gain traction in these non-union Southern state plants," he said.
"What I hope the American public understands is that those people who attacked this were attacking labour-management cooperation," King said.
