Leading figures in the industry said that manufacturers were looking to the British supply chain because of the prospect of expensive tariffs being imposed on cross-border trade.

At present almost two thirds of parts in British-built cars come from abroad, with the proportion as high as three quarters in vehicles such as the Vauxhall Astra. In some cases, parts are said to zig-zag across the Channel as many as 30 times during the production process.

With a clean break from the EU emerging as the most likely outcome of Brexit negotiations, industry sources said that a target…