Second quarter figures saw BCA’s index showed values fell by £390 compared to quarter one, from £5,772 to £5,332.
The report follows recent retail sales figures which showed a 3.9% drop in June, the sharpest monthly decline since 1986.
Values in the fleet & lease and part-exchange sectors also dropped by over 3% and nearly 5% respectively.
Tony Gannon, BCA communications director, said: "What is important is seeing if the market will bounce back in quarter three as it has in previous years.
"Ths makes next quarter's index figure critical for industry watchers hoping to predict the medium to long-term prospects for used car values - and by inference - used car demand."