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The production of popular UK-made cars from Mini, Jaguar, and Land Rover could be jeopardised by a post-Christmas exodus of mainland European workers, according to figures in the industry.

Between 20 and 40 per cent of workers in UK car manufacturing plants and component suppliers are thought to be from elsewhere in the EU, but uncertainty caused by Brexit could mean they return home in the coming months.

There is a particular concern that workers will not return to their posts after the Christmas break.

A number of factors may have combined to make UK manufacturing positions less attractive to overseas workers, including the 20 per cent fall in sterling since the referendum, as well as how welcome they feel in the country against the backdrop of Brexit.

A fall in domestic demand for new cars could also play a role, with new registrations down since April.

The Telegraph reported once source close to BMW as saying: “There's a real fear that they go home for Christmas and just don’t come back again. The euro has risen in value so the jobs here aren’t as attractive as they were.”

BMW, which runs the MINI plant in Oxfordshire and the Rolls Royce factory in Goodwood, employs 8,000 staff nationwide, of whom 500 are from overseas. The Rolls Royce site is particularly vulnerable to any exodus of staff, with 250 out of its 1,400 hailing from overseas.

One leading UK component maker said: “Every time something goes wrong with the Brexit negotiations another wave of people leave.”

The individual spoke anonymously over concerns future contracts could be put at risk by revealing how big the issue is. 40 per cent of the firm's workforce is from outside the UK.

They also said that the work experience they gained in the UK could make them highly employable in their own countries, while the fall in sterling has made their wage packet less appealing when converted to their home currency.

Any impact on component manufacturers would eventually affect the major car plants.

A report by the Automotive Council last year revealed there were 5,000 car manufacturing vacancies nationwide, but the present number of vacancies is thought to be considerably higher.