I dont think the intention was so much to increase the "green" fund rather than as Alistair said on the news to force the polluters off the road.
Trouble is the worst offenders will swallow up the increase without blinking an eye, they should just ban those vehicles full stop.
Yeah that will happen, not.
The government make 65% (I think) revenue on fuel, do they really want us running around in 1.0lt cars, of course not.
It's like the smoking dilemma, the govt make loads of money from smokers and don't really want them to stop which is why tobacco goes up every budget to make up for the loss in revenue from those who have given up since the last budget.