BERLIN (Reuters) - Former German President Christian Wulff was charged on Friday with accepting a bribe in exchange for a political favor, a year after a broader corruption probe forced him to resign from the largely ceremonial post.

Wulff was hand-picked by Chancellor Angela Merkel for the job of head of state in 2010. But he stood down after 20 months when prosecutors said they suspected he had accepted undue privileges and asked parliament to lift his immunity.

Lower Saxony state prosecutors suspect Wulff of lobbying Siemens AG to help market the film "John Rabe" after a movie producer paid Wulff's expenses during a trip to Munich's Oktoberfest beer festival in 2008.

The producer, David Groenewold, faces the same charges of corruption and bribery after footing a bill for Wulff totaling thousands of euros, the prosecutors said in a statement.

Wulff's lawyers said they would seek to clear his name.

"The charge of corruption ... is unfounded," they said in a statement.

One of Groenewold's lawyers told Reuters the charges did not come as a surprise. Earlier this week, they publicly maintained their client's innocence.

Wulff's reputation took a hammering in his time as president when top-selling newspaper Bild accused him of misleading the state assembly over a cheap home loan from a businessman friend. He later apologized for threatening the editor of Bild with "war" if he published the story.

Allegations about free flight upgrades, hotel stays and gifts further undermined his credibility. The media has even invented a new verb -- "wulffen", or "to Wulff", which means being evasive without telling a clear lie.

If convicted, Wulff theoretically faces from 6 months to five years in jail. But it is likely he would get probation.

The former president rejected an offer from prosecutors to settle the case with an out-of-court payment earlier this week.

(Reporting by Sarah Marsh and Thomas Seythal; Editing by Jason Webb)