The 27-country bloc has set manufacturers a goal of cutting emissions from new cars by around 15 percent by 2015, after a lengthy battle that pitted environmentalists against auto-making nations France, Germany and Italy.

“It can be important to try and review – did we go far enough at the time? Because this is a field where technology is really moving very fast,” Connie Hedegaard told a European Parliament hearing to evaluate her for the job of climate chief.

“Often we've seen industry will protest and say it's going to be extremely difficult, in fact it's almost impossible,” the Dane said. “But then it turns out that when we do these things, we can often do it quicker than assessed before, and claimed before, and they can do it even more ambitiously.”

Hedegaard said she would push for further work on cutting emissions from road freight, if parliamentarians approve her nomination when they vote on January 26.

“We still have not done what the EU should do on lorries. There will come an initiative on lorries, that will be one of the first things.”

It was unclear whether she was referring to existing EU proposals to improve the fuel efficiency of vans and light trucks by over 10 percent by 2016, or whether she planned to target heavier freight vehicles.