Birnbaum criticised legislators for being "passionately inert" with regard to Germany's energy transition away from fossil fuels and towards renewables, adding that this put the whole project at risk.

"To put it bluntly, we cannot afford this, because Germany is in the middle of the biggest transformation process since the industrial revolution," Birnbaum said.

"The energy transition is taking place all over the world. But Germany is making it particularly expensive, particularly bureaucratic and particularly cumbersome."

(Reporting by Markus Wacket; Writing by Christoph Steitz, Editing by Rachel More)