"You are beautiful. We should see each other,'' Mr Sarkozy is said to have whispered in the ear of Miss Trierweiler, who became France's first lady in 2012 but was dumped by Mr Hollande in January.
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The Paris Match journalist allegedly rebuffed Mr Sarkozy, later saying, "He's a cad,'' the book claims. Clearly annoyed, Mr Sarkozy is then said to have exclaimed: "Who does she think she is?''
The book alleges the incident explains the evident enmity between Miss Trierweiler and the former president since Mr Hollande's 2012 election.
French President Francois Hollande. Photo/AP.
That hostility was allegedly clear at Nelson Mandela's funeral in Johannesburg in December, where Mr Sarkozy is said to have cruelly quipped that Miss Trierweiler looked like Francois Mitterrand, the late Socialist president, in her oversized hat.
Mr Sarkozy's entourage is reported to have firmly denied the rumour about any pass, saying: "Valerie Trierweiler is absolutely not the former president's type.''