Image copyright AP Image caption Some 1,550 people work at Volkswagen's Chattanooga plant, which is the company's first US facility

In a surprise move, US workers have voted against union representation at a Volkswagen car plant in the southern state of Tennessee.

The vote derails efforts by the United Auto Workers (UAW) to organise foreign-owned factories in the southern US.

Experts had expected the ballot to pass in favour of unionising, after Volkswagen tacitly supported the move.

The vote had faced resistance from Republican politicians, who argued it would slow economic growth.

It was the UAW's first attempt in 13 years to unionise a plant not run by one of the three big US carmakers - General Motors, Ford, and Chrysler.

Analysts say the result could significantly curtail future organisation efforts and further dent the union's reputation.

Membership is reported to have plummeted 75% since the late 1970s, leaving it with barely 400,000 supporters.

'Outside influence'

Some 1,550 workers began voting at the plant in Chattanooga on Wednesday and rejected the union plan by 712 to 626 with an 89% turnout.

UAW spokesman Gary Casteel said "some outside influence" had been exerted on the poll.

Image copyright Center for Worker Freedom Image caption The Center for Worker Freedom purchased 13 billboards in Chattanooga opposing the vote

"There are still some issues that have to be sorted out about this election, and we'll let the people that do that evaluate the impact of others and whatnot further down the road," he said after the result was announced on Friday night.

Some believe the loss will make it harder for the UAW to recruit members at other southern plants.

Go South Image copyright Getty Images Eight plants have been opened by foreign car makers in the US in the past decade. With the exception of a Honda plant in Indiana, the rest have chosen to open in Southern states with right to work laws. They are: Nissan - Mississippi

Toyota - Mississippi and Texas

Hyundai - Alabama

Honda - Alabama and Indiana

Volkswagen - Tennessee

Kia - Georgia

"If they can't win this one, what can they win?" asked Art Schwartz, a former General Motors union negotiator following the vote.

The push for organisation started after Volkswagen opened its only US facility in Chattanooga in 2010.

The manufacturer's 61 other plants around the world have so-called "work councils", which represent employees' interests in daily dealings with management.

Mandated by law in Germany and popular in other European countries, works councils have never been tried in a US factory.

Prior to the ballot, VW's Chattanooga chief executive Frank Fischer said in a statement: "Our plant in Chattanooga has the opportunity to create a uniquely American Works Council, in which the company would be able to work co-operatively with our employees and ultimately their union representatives, if the employees decide they wish to be represented by a union."

Conservative groups had lead a fierce anti-union campaign in the lead-up to the ballot.

Opponents warned it would jeopardise Volkswagen's tax incentives and hurt the local economy by scaring away business.

Low wages have long been a selling point to lure big firms like Nissan and Boeing to the US south.