Car maker Toyota has raised questions over the long term future of its plant at Burnaston in Derbyshire - citing continuing uncertainty over the direction and timetable of Brexit negotiations.
News agency Reuters reported the Japanese firm's top foreign executive Didier Leroy warned they could be forced to shift some UK production elsewhere if concerns were not addressed.
Toyota announced plans in March to begin upgrading its Burnaston plant in preparation for future models at a cost of 240 million pounds, after receiving written assurances from the government.
But Leroy, attending the Frankfurt Motor Show, told Reuters the company could not wait indefinitely before deciding whether to build a new model at the site after production of the ageing Avensis model ends. Burnaston also builds the smaller Auris.
Britain’s car industry is increasingly anxious that its exports could face tariffs and other barriers after 2019.
Motor industry expert Professor David Bailey, of Birmingham's Aston University, said: