The Society of Motor Manufacturers and Traders (SMMT) is calling for an end to Brexit uncertainties that have sparked a significant drop in sector investment.
Here are some of the major firms raising their voices over the EU divorce:
Airbus - The plane manufacturer warned it could pull out of the UK with the loss of thousands of jobs if Britain leaves the single market and customs union in March 2019 without any transition agreement in place.
BMW - A senior director said post-Brexit delays in importing components would put operations under serious threat, potentially forcing UK closures.
Unilever - The company is moving corporate headquarters to Rotterdam in a major blow to the UK, although it has claimed the decision is not Brexit-related.
Siemens - The German firm's boss has warned time is running out to secure a Brexit deal.
Goldman Sachs - The firm is set to at least double its Frankfurt office to 400 staff through a mix of relocations and local hires, though other EU sites will also be expanded.
HSBC - It plans to move up to 1,000 jobs to France, where it already has a full service universal bank after buying up Credit Commercial de France in 2002.
JP Morgan - Around 1,000 front and back-office roles are likely to be relocated from London as part of plans to bulk up a number of EU offices.
Bank of America Merrill Lynch - Intends to relocate up to 125 UK staff to Dublin as part of its Brexit contingency plans.
Morgan Stanley - Understood to have plans to add around 200 staff in Frankfurt through a mix of new hires and relocations, with around 80 staff to be added to the bank's Paris office.
Jaguar Land Rover - The car giant is set to shift all production of its Discovery model to Slovakia from Birmingham in a move likely to affect hundreds of workers, although it has insisted it is not linked to Brexit.
EasyJet - The airline has applied for a new air operator's certificate (AOC) in Austria to allow it to continue flying in the European Union after Brexit, setting up a headquarters in Vienna.