Car registrations fell over a fifth in October, the steepest decline since May 2009.Registrations fell by 22.2% in the month to 131,495 units compared with last year's 168,942, according to the Society of Motor Manufacturers and Traders (SMMT),Last October experienced a boost from the government's scrappage scheme, representing 21.9% of the market, with 37,000 units."There was a significant fall in October's new car registrations, reflecting the impact of the Scrappage Incentive Scheme (SIS) at this time last year and some deterioration in consumer confidence", said Paul Everitt, SMMT's chief executive.However, if the SIS volumes are excluded, the industry remains on a par with last year's figures.Total new car registrations in 2010 are forecast to rise by 1.5% from last year, to an estimated 2.026m units."The industry expects the coming months to be challenging with slow, but steady, economic growth feeding through to improved confidence and demand during 2011."In the month, diesel car registrations grew by 3.8%, representing a record 54.7% of the market share. This is 13.7 percentage points higher than last October, when the industry experienced a large demand for small petrol cars as part of the SIS.The Ford Fiesta and VW Golf were the top two best sellers of October with 6,024 and 5,230 units sold, respectively.March and September remain the best months for car registrations, but the remainder of the year could see a pick-up in sales ahead of the VAT increase in January.