THOUSANDS of workers at BMW's Cowley plant are today being warned not to risk their jobs by voting for Britain to quit the EU.

Union bosses fear the firm may decide it makes "better economic sense" to move Mini production to Austria or Holland within a decade if the public backs Brexit in Thursday's referendum.

In a letter to sent union members today, Unite plant convenor Chris Bond will say: "Can we really afford to put the livelihoods of the 4,500 working here at Cowley at risk?"

It comes as David Cameron visited the plan yesterday and issued his sternest warning yet of the impact leaving the EU could have for the plant.

Speaking to the Oxford Mail, he added: "Today, 44 out of every 100 cars produced here go into the single market.

"If we made our access to that market less good, if we put ourselves at risk of tariffs and taxes, then plants like this could suffer.

"These are quality, skilled jobs and we want more of them in our country.

"And it’s not just the jobs here, it is the thousands of jobs in the component supply industry all over our country that are helping to produce this brilliant product."

His message will be echoed by Mr Bond, whose letter on behalf of Unite will go through letterboxes of thousands of workers today.

It will say: "BMW has made it very clear that it wants us to remain and I don't think for one second if the UK votes to leave the company would up sticks overnight.

"However, Cowley's future would become a lot more uncertain. Once we finish production of the new Mini, things could change very quickly.

"Minis are not just built in the UK. If we leave, the company may decide that it makes better economic sense to move production to the European mainland."

The message came as David Cameron made a last-ditch plea to voters in Oxfordshire during a tour of the Mini plant yesterday.

The Prime Minister repeated his warning that leaving the EU would raise the prospect of tariffs being placed on Minis shipped to the continent from Oxford and put workers' jobs at risk.

Mr Cameron said he hoped to see "a big remain vote in Oxfordshire", adding: "It benefits from having a strong university that receives European funding and from manufacturing and science-based jobs that clearly need access to the EU single market.

"Oxfordshire will be stronger, safer and better off if we remain in."

During his visit to Cowley Mr Cameron, also MP for Witney, helped put the finishing touches to a door on the Mini production line, using his tie to wipe away a smudge he left on the bodywork.

The PM, who was joined on the visit by former deputy Labour leader Harriet Harman, said he had a "very simple message" that "access to the European single market is vital for jobs in our country".

But Vote Leave accused the PM of "playing Project Fear" on people in Oxford.

Coordinator James Wakeley said: "David Cameron should be defending Britain, not talking our car makers down.

"The idea that the EU would place punishing tariffs on British cars is false. The EU has to comply with World Trade Organisation rules that prevent hostile tariffs.

"If we leave the EU and gain the ability to strike new trade deals ourselves, new markets will open for British industry, creating jobs and fresh opportunity for the Cowley plant and other British manufacturers.

"It is disappointing Mr Cameron is playing Project Fear on the people of Oxford, whose cars are bought because of their quality and not because of the EU."

Mr Bond said in his letter to Unite members that BMW has a base in Austria and pointed to the company's decision to start manufacturing the Mini Hatch and Convertible at VDL Nedcar’s plant in Holland.

Ian Robertson, a member of the BMW board, said: "We firmly believe Britain would be better off if it remained an active and influential member of the EU, shaping European regulations that will continue to impact the UK whatever the decision on Thursday."

The company has staff from more than 20 European Union countries who work at the Cowley plant.

His warning followed a statement from the Society of Motor Manufacturers and Traders, which said a vote to Leave would risk jobs with senior managers at firms including Jaguar Land Rover, Toyota and Vauxhall reiterating the warning.

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