Carmakers have warned that their factories, which rely on the constant delivery of parts to enter production cycles, would be severely damaged if Britain leaves the EU without a trade deal, forcing the need for customs checks at borders.

Honda said it had been assessing how to cope with any disruption caused by logistics and border issues following the departure on March 29.

"To ensure Honda is well placed to adjust to all possible outcomes, we are planning 6 non-production days in April 2019," a spokesman said.

"This is to facilitate production recovery activity following any delays at borders on parts. These contingency provisions have been put in place to best mitigate the risk of disruption to production operations at the Swindon factory."

Germany's BMW has said it will move the annual maintenance shutdown period for its British Mini plant to April, in case there is no trade deal.

(Reporting by Kate Holton; editing by Stephen Addison)