Sales of Volkswagen-branded vehicles fell 2.4% globally in November the wake of the emissions scandal, the German carmaker said on Friday.
The total for the 11 months of 2015 was down 4.5% compared with last year.
The annual tally was likely to fall short of last year's total as a result.
VW-brand board member Juergen Stackmann said: "In view of the current challenging situation, I don't believe VW will be able to make up the gap in the remaining days of the year."
Volkswagen said it sold 496,100 VW-brand cars worldwide in November.
Sales plunged in Brazil, with a 51.4% fall, and slid by 31.8% in Russia, although economic problems in both countries were largely to blame for those declines rather than the emissions scandal.
The VW brand delivered 6.12 million cars in total last year.
The company said last week that US sales fell 24.7% in November compared with the same month last year.
Volkswagen group chairman Hans Dieter Poetsch said on Thursday that a "chain of errors" led to the emissions scandal and that the entire company was now focused on regaining the trust of customers.
In September, US regulators found that some VW diesel cars had a "defeat device" - or software - to cheat emissions tests.
The company said the situation arose when it decided to launch a large-scale promotion of diesel vehicles in the US in 2005, but found it impossible to meet strict emissions limits in force in that country in time.
Mr Poetsch said: "No business justifies crossing legal and ethical boundaries."
Chief executive Matthias Mueller said he was confident that customers would overcome their reluctance to buy the group's vehicles in the coming weeks.
