Ever wondered about the competing pressures of making cars cleaner and more fuel efficient, at the same time as safer, comfier and faster?

Lawmakers, and a growing number of consumers, are demanding higher mpg and lower CO2 – figures which are reversed when you start adding the luxury, performance and safety features they crave. It’s a classic catch-22.

Fiat Auto boss Sergio Marchionne is one man who knows all about this conundrum. He’s busy lobbying the European Commission to make sure bureaucrats don’t impose untenable laws on a beleaguered car industry, forcing a Europe-wide average of 130g/km by 2012. And steep penalties for companies who miss the target.

“A target of 130g/km by 2012, through vehicle technology alone, is not feasible,” he says with a sigh of resignation. “It’s not that manufacturers have been standing still. Far from it. Average car emissions fell by 13% from 1995-2005. The problem is, their gains are being offset by rising vehicle weight.

“The majority of consumers are not ready to pay for fuel-efficient solutions,” adds Marchionne, taking a dig at hybrids like the Prius. “Highly CO2-efficient cars have met with very low demand despite considerable marketing efforts. Instead, buyers have opted for larger and safer cars, due to factors such as increasingly dense traffic, demographic trends and lifestyle changes.”

Marchionne claims cars are 16% lardier than 10 years ago and 10cm longer because of pedestrian safety measures.

To put that into perspective: between 1995 and 2005, the industry managed to cut average CO2 emissions by 40g/km – only for extra weight and safety measures to increase it by 15g/km. The net drop is a more modest 25g/km, Marchionne tells us.

It’s the first time I’ve heard this argument quantified. And it makes you wonder how much longer the lawmakers can really have their cake and eat it.