LONDON -- British car production rose 10 percent year-on-year in June but the SMMT industry association said growth was in jeopardy if the UK failed to secure unfettered access to the European Union's single market.
Britain's overwhelmingly foreign-owned automakers backed remaining part of the EU ahead of last month's referendum vote to leave the bloc, where over half of British car exports are sold.
Although production rose 10.4 percent to 158,641 units last month, the SMMT said this growth was due to investments made several years ago and future increases could be put at risk by Brexit.
"These decisions were based on many factors but, primarily, on tariff-free access to the single market, economic stability and record levels of productivity from a highly skilled workforce," SMMT CEO Mike Hawes said in a statement.
"To ensure the sector's continued growth, and with it the thousands of jobs it supports, these must be priorities in future negotiations," he said.
The SMMT, which surveyed its members between July 7 and 22, said nearly 70 percent were concerned about possible barriers to trade with the EU in any Brexit deal.
Sixty percent of the 289 SMMT respondents said a lack of certainty over the future status of skilled EU workers in Britain was a concern.
Inchcape, one of Britain's biggest car dealerships, said it expected the growth in new-car sales to slow in the months ahead amid uncertainty after the Brexit vote.
"Ahead of the EU referendum, the second-quarter new vehicle market growth rate moderated to 1.0 percent from 5.1 percent in the first quarter," it said. "We expect this moderation to persist into the second half," Inchcape said, as it posted an 8 percent rise in first-half pre-tax profit to 165 million pounds ($217 million).
UK new-car registrations fell for only the second time in over four years in June when Britain held its EU membership vote.