French President Nicolas Sarkozy threatened to "smash the face" of an editor whose magazine suggested that his wife Carla Bruni was a maneater, a new biography alleges.
The outburst came when Mr Sarkozy harangued the editor by phone for 40 minutes in January 2008, it is alleged.
Excerpts from the book by Le Point director Franz-Olivier Giesbert appeared in French media on Friday.
There was no immediate comment from the French presidency on the revelations.
Le Point ran an article by Patrick Besson giving "24 tips" to Mr Sarkozy ahead of his marriage to Carla Bruni, a former Italian supermodel.
One tip was: "Do not introduce your new wife to your sons, Barack Obama or any handsome men."
According to Mr Giesbert, Mr Sarkozy told him "this article is disgusting and I should smash your face in".
Mr Giesbert replied: "Are you threatening me?"
Mr Sarkozy reportedly hit back: "You deserve it. I don't know what's stopping me.
"What would you do if I wrote that your wife was a whore that slept with everyone and even wanted to have sex with your children? You'll see what I'm going to do to you."
Mr Giesbert's biography of Mr Sarkozy, called Mr President, Scenes from Political Life 2005-2011, went on sale on Thursday.
Before getting married Carla Bruni had dated rock stars, actors and other celebrities. Her former lovers are said to include Mick Jagger, Eric Clapton and Donald Trump.
Mr Giesbert writes that Ms Bruni herself defused the row, explaining to him that Mr Sarkozy was deeply in love and could not stand such things being written about her.