The car giant BMW has followed plane-maker Airbus in warning about the consequences of Brexit uncertainty.
BMW UK boss Ian Robertson says clarity is needed by the end of the summer.
BMW makes the Mini and Rolls Royce and employs about 8,000 people in the UK.
Earlier, Airbus, which employs 14,000 people in the UK, warned it could leave if the UK exits the single market and customs union with no transition deal.
The UK government says it is confident of getting a good deal for industry.
The customs union brings together the European Union's 28 members in a duty-free area, in which they pay the same rate of duty on non-EU goods.
Prime Minister Theresa May has ruled out staying in the customs union.
The UK is due to leave the EU on 29 March 2019.