UK car manufacturers are concerned that the Brexit could damage export levels, according to a report released by the Society of Motor Manufacturers and Traders (SMMT).

57.1% of SMMT members surveyed believed Brexit would have a negative impact on their businesses, with a further 27.7% uncertain at this early stage.

Though continuous growth led to a 16-year high for half-year production of 897,157 units, potential export barriers may risk future business, the SMMT said.

The increase in production was driven largely by the overseas market, with 77.8% of cars built for export, chiefly to the European Union. Year-to-date export demand grew 14.9% to 695,139 units.

The main concerns rested with the potential negative impacts of tariffs, customs charges, and other barriers between the UK and the EU single market, with 68.4% expressing this view.

The SMMT reported that 59.7% of respondents were worried about the status of EU nationals employed in the industry. A drop in sales was a concern for 52.7%, and falls in investment for 46.1%.

Mike Hawes, chief executive, SMMT said: “Europe is by far our largest market…investment 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,”

“To ensure the sector’s continued growth, and with it the thousands of jobs it supports, these must be priorities in future negotiations.”

Overall, British car manufacturers reported 11 straight months of growth in June. Production rose 10.4% to 158,164 units in June, and vehicles manufactured for the domestic market grew 7.1%.