BMW has warned that jobs could be at risk at its MINI production plants in the UK if the country votes to leave the EU in a referendum this summer.

In an email sent to all MINI and Rolls-Royce employees in the UK, parent company BMW outlined the potential risks to the UK business if members of the public vote to leave the EU in the recently announced referendum to be held on June 23.

The email said: “For BMW Group, more than half of Minis built and virtually all the engines and components made in the UK are exported to the EU, with over 150,000 new cars and many hundreds of thousands of parts imported from Europe each year.

“Tariff barriers would mean higher costs and higher prices and we cannot assume that the UK would be granted free trade with Europe from outside the EU.

“We get a significant benefit from the easy movement of our people between the UK and Europe. This allows the rapid transfer of expert knowledge throughout the Rolls-Royce Motor Cars and BMW Group networks, building the skill level of our UK workforce.

“Our employment base could also be affected, with skilled men and women from most EU countries included in the 30 nationalities currently represented at the home of Rolls-Royce at Goodwood.”

The firm’s main production base for the MINI is at Cowley in Oxford, with around 90 per cent of the pressings and almost 80 per cent of other parts such as doors, bonnets and tailgates made at Plant Swindon on Bridge End Road.

Following the arrival of the new MINI in 2001, around £60m was spent on the plant between 2004 and 2006 to prepare it for the production line. It is anticipated that a further £25 million is to be invested for more building and press line refurbishments.

A spokesman for the BMW Group said: “As a major employer, exporter and investor, the BMW Group is committed to the UK which is home to two of our brands, MINI and Rolls-Royce motor cars.

“Our experience shows that the free movement of components, finished products and skilled workers within the EU is extremely beneficial to British-based business.

“We firmly believe Britain would be better off if it remained an active and influential member of the EU, shaping European regulations which will continue to impact the UK whatever the decision in June.”

One former Plant Swindon employee who clocked up 38 years of service on the production line said he hoped BMW’s UK workforce would not be adversely impacted by any outcome of the referendum this summer.

He said: “I cannot see them – after all of the investment they have put into their engineering plants – pulling out completely. Restructuring, yes, but pulling out, I just cannot personally see it.”