Stephan Mayer said he had personally decided to step down on "health grounds".
The deputy leader of Germany's regional conservative party has resigned after insulting and threatening a journalist.
Stephan Mayer said he would officially step down as secretary-general of the Bavarian CSU party on "health grounds".
But his departure comes after the 48-year-old had a verbal altercation with a journalist from the magazine Bunte.
German media say that Mayer took offence to a "clearly illegal" magazine article about his private life which mentioned an illegitimate child.
"I will destroy you. I will find you, I will pursue you to the end of your life," he told the journalist, according to Bild.
The publisher of Bunte magazine said the threats were a "violation of the rules of the democratic game and of the political culture of our country".
On Tuesday, Mayer -- who was only appointed head of the Bavarian party in February -- said he "deeply regretted" his choice of words.
"In an interview with a Bunte journalist because of a clearly illegal article, I may have used a choice of words that in retrospect I would not consider appropriate," he said.