"That does not exclude - if we are serious about wanting to assure durable development - of considering new political measures that would be aimed at reducing pollution and conserving energy resources, at stimulating development and the introduction of new technologies, for example by an energy tax or also by an ecology tax," he said.

Goebbels said the introducting of such taxes should be handled by the European Union. But the introduction of similar measures in Denmark and the Netherlands had not resulted in a mass exodus of investments or a loss of competitiveness.

"Personally, I remain convinced that voluntary agreements for a more efficient use of energy should continue to remain at the forefront," Goebbels said.

"But it is also true that voluntary agreements should remain confined to the subsets defined and limited by our economy."