Cars’ carbon emissions and consequent vehicle excise duty (VED) rates are expected to become as influential on used car choice as fuel economy or insurance costs.

Industry valuation experts CAP is to start publishing CO2 figures and related tax bands in its Black Book residual values, prompted by the potential impact of proposed VED rates to be introduced next year.

CAP believes the mounting costs of VED will lead to many older cars losing value more rapidly as buyers take into account the cost of taxing them.

Mark Norman, CAP’s operational development manager, said cars emitting more than 180g/km of CO2 will be the hardest hit, and will mean the annual cost of a tax disc could, in some cases, represent more than half the value of the car itself.

For example, a 2001 Y-registered Fiat Marea 20V ELX saloon has a trade value of around £650, but under next year’s proposed VED rates will cost £415 to tax for 12 months.