Perhaps that's the way out. Provided that either the manufacturer or consumer can offset the carbon through whatever means then they can still produce higher C02
I can see it now. Property speculators buying up land to be turned into forests
Seriously though all
of the car companies, and a lot of the consumers aren't going to like this. They'll take some convincing, and the government that goes along with it won't get voted back in.
It's the same with road pricing. It'll take some balls for any government to introduce it knowing that it'll lose them the next election.
Until public transport is a viable alternative we'll all be wedded to our cars. In the Great British tradition we'll moan, groan, but ultimately pay up.