Car industry leaders have backed the Remain campaign in the week of the EU referendum.
A statement from the Society of Motor Manufacturers and Traders said a vote to Leave would risk jobs.
The group's chief executive Mike Hawes told the BBC that leaving the EU would "jeopardise" the industry's continued success.
He said: "Remaining will allow the UK to retain the influence on which the unique and successful UK automotive sector depends."
The BBC reported that directors at Toyota UK, Vauxhall, Jaguar Land Rover and BMW, as well as from component makers GKN and Magal Engineering, also backed the Remain campaign.
Roy Harvey, chairman of Vauxhall, said leaving the EU would be "undesirable" because the industry benefits from the free movement of goods and people.
Vote Leave said British cars are increasingly being exported outside the EU and Brexit could provide a "boost" to the industry.
A report by the Economist Intelligence Unit earlier in June said UK car sales will decline "over the next few years" if there is a vote to leave the EU.
Prime Minister David Cameron said in a message on Twitter: "The UK car industry is clear - we should remain in the EU for a strong economy."
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