The number of cars delivered by Volkswagen fell nearly 20 per cent last month due to the introduction of new emissions testing rules, the manufacturer said.
A total of 485,000 vehicles were delivered throughout the world in September, 18.3 per cent down on the same month last year, with Europe experiencing a severe fall following the introduction of the new Worldwide Light Vehicles Test Procedure (WLTP) rules.
Germany was hit the hardest by the changes and saw deliveries fall by 47.1 per cent last month to 23,300 cars.
The new WLTP laboratory test, which was implemented at the beginning of last month, measures the fuel consumption and CO2 emissions from passenger cars, and replaced the New European Driving Cycle (NEDC).
Volkswagen sales board member Jurgen Stackmann said: "The year to date has been the most successful ever for Volkswagen.
"Developments in September were a setback, but we had been expecting this following the records in the summer. October will also be affected by the changeover to the WLTP test procedure.
"Currently, we have obtained WLTP approval for high-volume variants of all 14 Volkswagen brand models. By the end of the year, the changeover should have been virtually completed.
"This is why we expect a return to our old strength. From November, we will be ready for the end-of-the-year sprint in Europe."
Jaguar Land Rover (JLR) also reported a drop in its September sales figures yesterday as it announced a two week shut down of its Solihull plant.
JLR sold 57,114 cars in September, a 12.3 per cent year on year drop, with the firm shipping almost 20 per cent fewer Land Rovers than September 2017.
Chinese sales nearly halved, falling 46.2 per cent, with JLR blaming import duty changes and trade tensions for hurting consumer appetite.
Sales also fell almost five per cent in Europe thanks to reduced demand for diesel cars, though UK demand slipped less than one per cent.