With the European Union pushing to mandate a blanket 130g/km average fleet limit for CO2 emissions per car brand by 2012, Porsche has made waves this week by saying that if such a proposal was accepted, it could be forced to close its doors.

That won't happen, of course. The company is just too big and influential for that these days; remember that it's the majority shareholder of Volkswagen, Europe's largest car-maker, and parent to Audi, Bentley, Lamborghini, Seat and Skoda no less. But chairman Wendelin Wiedeking has begun to ramp up his opposition to the controversial EU proposal, which he says discriminates against makers of more overtly sporty cars.

His suggestion – and it is a good one – is a graduated plan whereby each class of car would be given a different CO2 limit to meet, with smaller, low-powered cars set lower limits than larger, more powerful cars.

It makes sense, though I can see problems in trying to classify various cars; is a Mercedes-Benz R-class a luxury sedan or an MPV, for example? As Wiedeking pointed out, "it is just not technically possible for a car like a 911 to meet the same levels of CO2 mandated for a Polo."

He added: "Can you imagine the uproar if luxury home owners across Europe were told they weren't allowed to continue living in their homes because they consumed too much energy and that they should move to a smaller home. That's basically how they are treating car drivers. They're saying you shouldn't drive a 911 because it puts out more emissions than a Polo. That's pure discrimination."

I have to say I agree with him. I'm all for lowering CO2 limits – we all should be. But the European Union shouldn't act alone in mandating laws. It must listen and work with the car-makers to set realistic limits. Without them, we'll get into a situation where they will simply be ignored. And that's a situation we don't want to get into.