Figures show that an average two year old vehicle now has a value of 65.4% of its original price compared to 65.9% 12 months ago.
'Overall two-year values are performing worse than three-year values at present, the only exceptions being the UK and Portugal,' said eurocarprice.com.
It says that diesel models have consistently achieved lower depreciation rates than petrol models, with diesel noting an average residual value of 67.5%, compared to 64% for petrol models.
'However,' the study warns, 'as for three-year values, the gap is narrowing with average diesel values declining by 1.4% whilst petrol models have increased by 0.9%.'
It found that upper medium diesels are experiencing the largest declines, with the value of Ford Mondeo, Nissan Primera and Peugeot 406 dropping by more than 5% over the past 12 months and Citroen Xantia and Renault Laguna dropping more than 10%.