BMW has joined Honda by warning of the “nightmare” scenario of delays to shipments at British customs posts caused by Brexit, according to reports.

The motor giant, which produces MINI parts at Plant Swindon, is among global firms that have raised concerns about the free-flow of trade outside the EU.

Honda has already told MPs that a single 15-minute customs delay without a frictionless arrangement with Europe could cost £850,000 a year.

Millions of components from around the world are delivered to car factories in Britain, with vehicles exported the other way, and hold ups could impact on strict ‘just-in-time’ delivery systems.

The Department for Business, Energy and Industrial Strategy committee found that Brexit is an exercise in “damage limitation” for the UK car industry, with its survival dependent on maintaining smooth trade links.

Executives from leading car manufacturers told Reuters at the Geneva Motor Show that they are already drawing up plans to warehouse supplies ahead of the departure date on March 29, 2019.

Peter Schwarzenbauer, a member of the board of management for Mini, said: “We don’t know if each truck gets held up. We can build up bigger stocks so that we are more flexible in production.

“It is a nightmare right now.”

Honda, which has a plant in South Marston, was also said to be drawing up stockpile plans to safeguard their delivery chain against possible disruption after Brexit.

BMW Group has a production site in Stratton St Margaret comprising a press shop serving both Mini and BMW and a sub-assembly producing doors and tailgates. Over a million parts are pressed every week, with about two thirds for MINI and the rest of the wider global BMW Group network.

The Government is trying to arrange a transition deal that will maintain the current trade system after the Brexit date until 2020 or 2021, and Theresa May has outlined plans to protect the frictionless movement of goods between the UK and Europe. However, Honda and BMW are said to be among companies considering extra warehousing to hold larger stocks of components to protect production from customs delays in the event that free-trade agreements are not struck.

Executives at BMW joined representatives from some of the largest European countries at Downing Street today/yesterday (THU), where they were expected to voice concerns about maintaining supply chains outside the EU’s tariff-free customs union, according to reports.

Meanwhile, diggers have been moving the earth at BMW’s site in Stratton St Margaret today as a dilapidated building was demolished.

The motor giant has no specific plans yet as to how the area off Bridge End Road will be used in future. A spokeswoman said: “The redundant building had been empty for 10 years and was becoming increasingly dilapidated and was no longer needed.

“The project started in November last year and will continue to around August this year."