The moves are aimed at ensuring plants, which rely on the just-in-time delivery of tens of thousands of components, can keep operating after Brexit on March 29, but will add costs and bureaucracy which could risk their long-term viability.

London and Brussels hope to agree a deal by the end of the year to avoid tariffs and trade barriers, but Prime Minister Theresa May’s proposals have been criticised by both Brexiteers, who want a cleaner break from the bloc, and the European Union.

McLaren Automotive is looking at having its cars certified by both a British and an EU agency to smooth sales. It is also planning to stockpile critical components and change shipments into the EU around Brexit if there is disruption.

“I will sell a little more in January and February and plan to pick the volume up in May and give us a leaner period through the change point,” Chief Executive Mike Flewitt told Reuters.

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