Scandal-hit German President Christian Wulff has resigned as head of state, a day after prosecutors asked parliament to lift his immunity from prosecution.

"I am ... today stepping down from the office of federal president to free up the way quickly for a successor," he said in a televised statement from his Bellevue palace.

Over the past two months Mr Wullf has become embroiled in a scandal over money, power and political favours that could damage Chancellor Merkel who installed him in the largely ceremonial office in 2010.

"The state prosecutors of Hannover now have enough actual indications and therefore the start of a suspicion of [the] acceptance of favours," the prosecutors wrote in a statement released last night.

"Therefore they have asked the President of the German Bundestag to lift the President's immunity."

Hannover is the capital of Lower-Saxony, where Mr Wulff was state premier from 2003-2010.

German presidents have limited formal powers but Mr Wulff's nine post-war predecessors managed to become popular leaders as a voice of higher authority.

The President is supposed to embody the nation's conscience largely via speeches and moral suasion.

Apology for misleading parliament

Mr Wulff belatedly apologised for misleading the Lower Saxony state parliament about a cheap €500,000 home loan from a businessman friend.

He also apologised for leaving a message on the answering machine of the editor of Germany's best-selling Bild newspaper threatening a "war" if the daily published a story about his private finance dealings.

He was also later criticised for accepting free upgrades for holiday flights for himself and his family as well as staying free of charge at the holiday villas of wealthy businessmen.

The head of the German parliament's immunity committee Thomas Strobl told daily Die Welt it could possibly debate a request to lift the President's immunity during the next parliamentary session on 27 February.

"The (Social Democrat) SPD will agree to this request," SPD parliamentary floor leader Thomas Oppermann told Die Welt.

The prosecutors said the aim of their request was to be able to pursue their investigations in a formal procedure.