(Reuters) - Germany's nuclear lobby is mulling plans to take the German government to constitutional court, to halt the country's nuclear exit and seek billions in damages, the online edition of Der Spiegel said on Sunday.

A legal opinion commissioned by utility E.On has concluded that the German government's plan to exit nuclear energy by 2022 is unconstitutional, Spiegel's Web site said.

The legal opinion, which was prepared for E.On by law firm Gleiss Lutz, says Germany's current energy strategy infringes on basic property rights enshrined in Germany's constitution, Der Spiegel said, citing a copy of the document.