There's already confusion about where British carmakers can get their new cars approved to go on sale.

The European Automobile Manufacturers’ Association (ACEA) is calling for EU negotiators to pay close attention to regulations on new car type approval, with concerns that the UK introducing its own system could cause issues across the whole of the motor industry.

The big worry is that cars approved in the UK will no longer be eligible for sale in mainland Europe, and likewise EU-approved cars in the UK. Currently, the European Union has an approval system that allows cars approved by national bodies within the Union to be sold anywhere within it. Now the ACEA is pleading for the UK and EU to mutually recognise each other’s vehicle approvals after Brexit. For that to happen though, the UK would need to maintain all EU legislation regarding car production.

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'It is essential that manufacturers can maintain valid type approvals in both the EU and the UK as of 30 March 2019, no matter where the approval was issued,' said ACEA secretary general, Erik Jonnaert. 'We are therefore calling on the European Commission to clarify how existing approvals can be transferred from an EU27 authority to the UK, and the other way round.'

The UK's commitment to maintain 2021 EU targets regarding CO2 emissions also remains a potential stumbling block. Currently, the EU tracks CO2 data from all newly produced cars in the Union, but when Britain leaves, it will no longer fall under that rule, nor will it have to meet the targets.

'Excluding UK data from the CO2 calculations would leave very limited time for the industry to readjust compliance strategies for reaching the stringent 2021 targets,' said Jonnaert, insisting that the ACEA wants Britain to maintain the current system, even after Brexit.

It's not just automotive legislation that the ACEA wants to maintain. Currently, the automotive industry works on a ‘just-in-time’ and ‘just-in-sequence’ scheme, and were deliveries to be held up at customs, it could cause not only a delay, but increased costs too.

'The UK deciding to remain in a customs union with the EU would of course be an effective solution to enable frictionless trade in goods between the EU and UK,' Jonnaert explained.

'But, regardless of which Brexit scenario is pursued, it is essential that EU and UK authorities already now start preparing to simplify customs procedures and to reinforce their customs capacity. Otherwise we will see severe land and sea-port congestion at both sides of the Channel once the UK leaves the EU.'

There is also the potential for hefty tariffs to be placed on vehicles, such as 10 percent for cars, and between 10-22 percent on commercial vehicles.