Car giants Toyota and BMW have issued stark warnings about the impact a no-deal Brexit would have on their plants in the UK.
The future of the Mini factory at Cowley, near Oxford, would be thrown into doubt if there is a no-deal scenario, parent company BMW said.
The German firm said production of Minis could be moved to Holland if the UK crashed out of the European Union without a deal on March 29.
And Toyota warned that a no-deal Brexit would make it “extremely complicated” for the Japanese firm to build new models in the UK.
Speaking at the Geneva Motor Show, Graham Biggs, corporate communications director of BMW Group UK, said he could not give “any guarantees as to the future of the Oxford plant”.
He said: “In the event of a no-deal Brexit, some or all of the production of the Mini could be moved to Holland where we have a plant.
“We need frictionless trade and a no-deal Brexit will not give us that from what we can see.
“Nothing is certain. I cannot give any guarantees as to the future of the Oxford plant. No company can.
“I cannot make any promises to the workers because at the moment we just don’t know. But what I can say is we are heavily invested in the UK.”
Even if there was a deal, “no promises could be made” as “nothing is certain”, he said, but added: “We are pressing for a deal and that’s what we’d like to see.”
Meanwhile, Didier Leroy, chairman of Toyota’s European operations, said a no-deal outcome to EU withdrawal talks would be “terrible” and would create “big additional challenges” to UK operations’ competitiveness.
His comments came after Honda announced that it is closing its plant in Swindon and Nissan ditched plans to produce the X-Trail SUV in Sunderland, though both companies said the decisions were driven by factors other than Brexit.
Toyota began production of its new hybrid-powered Corolla model at its plant in Burnaston, Derbyshire, in January.
Mr Leroy told the Financial Times that the £240 million investment in the model was made on “significant trust in the UK that they would be able to achieve a good deal in Europe”.
He stressed that Toyota had “no plan today to withdraw from the UK and stop production”.
But he added: “If we don’t have access to the European market without a specific border tax, it seems to be extremely complicated to think about … introduction of another model.”
Mr Leroy told the FT: “No-deal is terrible, it will create big additional challenges to keep competitiveness.”
He said Parliament had “to decide what’s best for employment” when voting next week on whether to leave without a deal, urging MPs: “Don’t create a huge mountain.”
Theresa May’s official spokesman said the Prime Minister believes the best way to deliver the certainty which car companies want is for MPs to approve her Withdrawal Agreement in the “meaningful vote” due to take place by March 12.
The spokesman said: “The PM fully understands that businesses need more certainty and for us to secure a deal which allows us to protect those just-in-time supply chains and deliver frictionless trade.
“That’s why we are working hard to secure the changes which MPs need in order to be able to support the meaningful vote.
“Only by passing the meaningful vote will we be able to deliver that certainty.”