UK car production output fell by 5.8% in September and commercial vehicle (CV) production fell by 20.2% over the same period.
The latest figures from the Society of Motor Manufacturers and Traders (SMMT) shows that car production is still up by 10.2% over the year-to-date despite the fall in September.
However, CV output is down 7.5% over the year so far.
UK engine production declined 12.8% in September, with January-September levels down 0.4%.
Paul Everitt, SMMT chief executive, said: "Declining demand for cars and vans across the major European markets impacted UK vehicle and engine production in September.
"Total UK vehicle manufacturing in the year so far has increased 8.7%, but monthly output fell by 7% in September.
"The strong demand for UK products outside Europe and the investment committed by major vehicle manufacturers will secure future growth, although the coming months will be challenging for companies at all levels in the supply chain. European governments must focus on securing financial stability and economic growth or they risk long-term damage to key industries."