Cars sold by BCA fell in value to an average of £6,714, the lowest recorded since December 2006.
Performances against CAP Clean also fell – to an average of 94.2%, the lowest since January 2006.
Fleet and lease values have now fallen for two months in a row.
In November they were £293 down on October, and £631 behind September.
However, year on year, November’s values were up by £190, or 2.9%.
Tony Gannon, BCA’s communications director, said: “These latest figures will surprise no one who has been selling used cars in the wholesale market over the past few weeks.
“The market has got significantly harder and while values soared to new record levels in September, we warned then about an underlying softness in demand.
“Fleet values stalled in October as increasing volumes hit the market from fleet operators and leasing companies.
There were growing signs of a two-tier market as well-specified, retail-quality cars found a ready audience of buyers, but average stock in average condition was more difficult to sell.”
Mr Gannon said the same was true in November, and underlined the weaker market.
“The performance against CAP suggests there is some pragmatism among fleet and lease sellers and an understanding that the best bid may well be short of CAP Clean,” he said.