Sir – My feeling that we have too many unnecessarily large and environmentally damaging vehicles was confirmed on television.

It was then reported that of new vehicles, those purchased in Oxfordshire emit on average much more carbon dioxide than those of any other county. This is not a statistic we should be proud of.

The present system of taxing vehicles on the basis of carbon dioxide emissions is on the face of it very pro-environment.

But in practice it extracts more tax from poor people who manage to pay for an “old banger” with high emissions, than from richer people who buy bigger newer cars.

It would be fairer if motor car tax were based also on the volume of the vehicle, and if tax rates increased more steeply with emissions and size than at present.

John Killick, Abingdon