Average ex-finance and fleet vehicles saw an increase in supply and drop in demand during October, according to G3 Remarketing.
The average price of ex-finance vehicles dropped roughly 5% month-on-month to £6,531, with ex-fleet vehicles down 2.79% to £8,746.
Matt Dale, director of G3, highlighted the Ford Fiesta and Focus, Citroën DS3 and Vauxhall Insignia as seeing "significant drops".
Meanwhile, Dale said the first cars from the 63-plate registration were entering the supply chain and stock volume had increased 10% during the month.
"Volumes are expected to plateau in November, but with overall rates dropping, this will have a detrimental impact on values until early January," said Dale.
MPVs have seen a surprise increase in price while cheaper small cars have remained buoyant.
While nearly new Vauxhall Zafira Tourers held a return of 103% CAP Clean, Renault Clios, Vauxhall Corsas and Citroën C1s priced between £3,000 and £4,000 averaged 101%.