"Whoever builds coal power plants today needs to be aware of the fact that such a policy will be expensive in the long term," he said in the interview, which will be published in full on Sunday.

"From a middle term perspective, only coal power plants with environmentally acceptable technology ... should be operated."

German utilities plan to put at least 26 new coal plants on line in the coming years.

The German environment ministry has prepared plans to require to force brown coal power plants to reduce their carbon dioxide emissions as part of an overall plan to cut emissions.