Since 1980 Member of the German Bundestag
Member of the Committee for Foreign Affairs
Deputy member of the Committee on the 
Environment, Nature Conservation and Nuclear Safety.

Since 1987 Member of the Parliamentary Assembly of the Council of Europe

Since 1988 Honorary President of EUROSOLAR - The European Association for Renewable Energy

Since 1989 Editor of the magazine "Solarzeitalter - Politik und Ökonomie Erneuerbarer Energien" on policy and economics of renewable energy

Since 1997 Editor of the magazine "Zeitschrift für Neues Energierecht" (ZNER) on juridical questions of energy

Since 2001 Founding General Chairman of the World Council for Renewable Energy (WCRE)

Since 2004 Chairman of the International Parliamentary Forum on Renewable Energies

1991 - 1993 Chairman of the Arms Control and Disarmament Committee of the German Bundestag

1994 - 1997 Chairman of the Committee on Agriculture of the Parliamentary Assembly of the Council of Europe 

Since 1993 Member of the Federal Board of the Social Democratic Party (SPD)