Actually the real point was made on the Beeb by IIRC Jeremy Vine.
No one who buys a 50 grand NEW car gives a toss about the VED.
People on tight budgets aren't going to buy new cars: they may want or need to run an older car that is pretty thirsty, on low mileage, simply because they have it already.
Why tax the car and not the fuel? because that way you can gouge a certain class of people. Irrespective of their actual income, or their ability to pay.
If fuel duty is a fundamental part of eco bollox, why is domestic heating oil and red diesel not taxed to the same extent, or gas?
I estimate that by this logic everyones domestic fuel bill should double.