There were 13,970 VW registrations last month, compared to 15,495 in October 2014, the Society of Motor Manufacturers and Traders (SMMT) said.
Seat and Skoda sales – two other VW brands – were down 32.2 per cent and 3 per cent respectively.
But other manufacturers also saw declines as sales for the industry as a whole fell by 1.1 per cent, the first drop since early 2012.
This suggests the emissions crisis has not hit VW sales particularly hard yet.
Vauxhall sales were down by 16.4 per cent, Nissan by 12.9 per cent and Mitsubishi by 11.9 per cent.
But year to date figures for the UK industry are up 6.4 per cent compared to this time in 2014.
SMMT chief executive, Mike Hawes, said: “The UK car market has gone through a period of unprecedented growth and, so far, 2015 has been a bumper year with the strongest performance since the recession.
“As expected, demand has now begun to level off but the sector is in a strong position, as low interest rates, consumer confidence and exciting new products combine to attract new car buyers. The current full-year growth forecast remains on track.”
VW admitted in September that it fitted sophisticated software to cheat emissions tests for nitrogen oxides in 11 million diesel vehicles worldwide, including almost 1.2 million in the UK.
It set aside £4.8 billion to deal with the controversy, and chief executive Martin Winterkorn resigned.
Luxury brands bucked the overall year-on-year trend, with Aston Martin sales up 40 per cent, Bentley up 29 per cent, and Porsche – part of Volkswagen – showing a 20.7 per cent rise.
A motoring expert claimed the SMMT figures for Volkswagen were probably caused by industry conditions rather than the diesel scandal.
Jim Holder, editorial director of magazines Autocar and What Car?, said: “I think it’s more about a slowdown in the industry as a whole.”