The prosecutors in Lower Saxony, where Mr Wulff, 52, was previously premier, said there was an "initial suspicion" that he improperly accepted benefits.
He has also been accused of trying to bully a paper not to run the story.
The president - whose primary role is to serve as a moral authority for the nation - denies any wrongdoing.
The widening row is seen by analysts as a blow to Chancellor Angela Merkel, who helped Mr Wulff to secure the largely ceremonial office in 2010.
Angry message
On Thursday, prosecutors in Hannover, capital of Lower Saxony, said in a statement there were "enough actual indications" that the president had acted improperly.
"Therefore they have asked asked the president of the German Bundestag (the lower house) to lift the president's immunity."
The move is formally required to start proceedings against Mr Wulff, although this does not mean necessarily that he president will be charged. » | Thursday, February 16, 2012
