BERLIN (Reuters) - German President Christian Wulff refused on Thursday to approve publication of a potentially explosive voicemail message he left on the phone of a top newspaper editor, in an escalating scandal that could cost him his job and damage Chancellor Angela Merkel.
The move came a day after Wulff went on television to try to defuse the uproar over his apparent attempt last month to pressure Germany's top-selling paper Bild to kill an embarrassing story about a private home loan he secured in 2008.
German media and opposition lawmakers have stepped up attacks on Wulff, who in the television interview made clear he had no plans to step down but admitted to making a "grave mistake" by leaving a threatening message on the voicemail of Bild editor Kai Diekmann.
Merkel backed Wulff for the presidency in 2010 and the outrage over his conduct risks becoming a major distraction for her at a time when Berlin is preoccupied with solving the two-year old euro zone debt crisis.
Keen to avoid the distraction of a prolonged and divisive debate about a successor, Merkel has supported Wulff until now, even as calls for his resignation have mounted, mostly in the German media.
In the television interview, Wulff rejected claims that he had sought to quash the home loan story, saying he only wanted to delay its publication by a day to give him time to respond.
Bild disputes this version and Diekmann wrote to Wulff on Thursday asking his permission to release a transcript of the message, in which Wulff threatened the paper with "war" and legal consequences if it went ahead with the story, according to media reports.
"My message, given in an unusually emotional context, was destined for you and no one else," Wulff said in a response to Diekmann that was released by his office.
Bild said it regretted Wulff's decision to keep the contents secret, saying it flew in the face of the president's promises in recent weeks to be fully transparent on details of the scandal.
Benno Poeppelmann, a legal expert at the German Association of Journalists DJV.L, told Reuters he saw a strong argument for classifying Wulff's phone message as non-private, meaning Bild could release excerpts from it without the president's approval.
Despite the voicemail message from Wulff, a longtime party ally of Merkel, Bild went ahead and published its story in mid-December.
In it, the paper reported that Wulff had received a home loan in 2008 at cheap rates from the wife of a wealthy businessman friend Egon Geerkens when he was conservative premier of the northern state of Lower Saxony.
He is accused of misleading the state parliament when he denied having any business links to Geerkens and his critics say he may have also broken ministerial law.
Germans take the office of president seriously. The person in the post is expected to act as a moral authority for the nation, defending constitutional laws, including a commitment to press freedoms.
Public support for Wulff has fallen to 47 percent from 63 percent in a matter of days, a poll by ARD television showed.
Wednesday's television appearance, in which he portrayed himself as the victim of an aggressive media, was not enough for many newspapers which said the scandal was not over.
"The affair is not over with this television interview. The president has not won back the moral authority that enables him to exercise his office," wrote the Financial Times Deutschland, striking a similar tone to other papers.
While most politicians in Merkel's conservative party welcomed his statement, opposition members were more critical.
"The Wulff affair is not over," said senior Social Democrat lawmaker Thomas Oppermann. "The embattled president is becoming an increasing burden to Chancellor Merkel who chose him. Mrs Merkel must make clear that his behaviour is damaging the dignity of the office."
Reporting by Madeline Chambers; Editing by Noah Barkin