Sean O'Grady: The industry gets the blame. But consumers keep buying bigger cars

It's very easy to blame the car lobby for trying to put the brakes on environmental progress but there is every reason for Europe's consumers to indulge in a little soul-searching too.

It is true that every time the European Commission has proposed new measures to tighten up on emissions, on safety, and on recycling, the powerful motor industry lobby has screeched with anguish, as if the Commission had done something as rash as a handbrake turn on an autobahn. Yet, on every occasion, the car makers have moved up a gear and delivered - cleaner, more efficient, safer and better performing vehicles.

They've coped with the abolition of leaded fuel; with compulsory catalytic converters; and with the successive Euro I/II/III/IV rules on engine design. The engineers and designers should actually be congratulated on that.

The improvement is remarkable: Ford say their Focus emits 26 per cent less carbon dioxide than the equivalent Escort model they made a decade ago. At the other end of the market, a Mercedes-Benz CL Coupe with a big V8 engine is 15 per cent greener now than it was five years ago. The manufacturers are obliged to take their green obligations seriously - even if they rarely welcome them.

We consumers, however, are free to choose. And we choose the wrong kinds of cars. Taking the UK's record, if the pattern of our car buying had remained as it was in 1997 the average CO2 emissions for new cars would probably have met even the latest EU target of 130g/km. Instead of a drop of about a quarter, the average carbon dioxide emissions of new cars sold only fell by 12 per cent, to 167g/km in 2006.

That discrepancy is accounted for by our changing tastes: we now buy relatively fewer small hatches and saloons, and more heavy SUVs and people carriers. Our prosperity means we can afford to buy bigger, better cars with bigger engines, and we do. So when a 1.8 litre Vectra might once have sufficed for an aspirational family, now they can afford a 3 litre BMW.

Even though those individual models are much more green than their predecessors, our relentless demand for upmarket and larger transport has partially negated the progress the car makers have made. Yet small cars are better engineered than ever before, and easily surpass even the new "tough" EU target.

Some small diesel Fords, Citroens and Fiats will better 120g/kg, with commensurate fuel economy, and still top 100mph. But will we trade down? EU Commissioners aren't the only ones who like their transport to be as stylish, comfortable and large as possible.