The Society of Motor Manufacturers and Traders (SMMT) said the reduction came as car companies were gearing up for new models and temporary supply chain constraints restricted output.
A total of 65,478 vehicles were made in July, with four in five cars produced destined for customers overseas.
The largest markets by volume were the EU (51.3% of exports), the US (17.6%), China (8.6%), Turkey (5.5%) and Japan (3.1%).
SMMT chief executive Mike Hawes said: “Following significant growth last year, some readjustment in output was to be expected.
“Indeed, an ongoing degree of volatility is likely as the industry restructures to transition to zero emission vehicle production.
“As the billions already committed to new models start to deliver a return, volume growth will resume, providing we seize every opportunity to enhance our global competitiveness.
“We need investment in skills, healthy markets, cheaper green energy, and fair trade deals that help British-built vehicles reach international customers more easily, all of which should be wrapped in an overarching industrial strategy that ensures automotive continues to be a key driver of economic growth.”