Femme fatale Mata Hari was beautiful, a compulsive liar, and without morals — but she wasn’t a spy and suffered from syphilis contracted from her husband not her promiscuity, according to a new biography.

After pouring over declassified and other papers about the Dutch-born exotic dancer and courtesan, author Pat Shipman sided with growing research that Mata Hari was used as a scapegoat by the French who convicted her of espionage and executed her during World War I to bolster national morale.

At her trial it was charged that she was responsible for the deaths of at least 50,000 French soldiers after she passed secrets from Allied officers and officials to the Germans.

“But the evidence is quite strong that she was completely innocent of espionage,” Shipman, a professor of anthropology at Pennsylvania State University, told Reuters.

Shipman said Mata Hari’s standing in 1917 was similar to that of Marilyn Monroe in the 1960s — she was recognisable everywhere and considered the sexiest, most desirable women in Europe.

“This is part of why it is so ludicrous to think she was a spy. She couldn’t be clandestine and sneak around. She couldn’t help but attract attention,” said Shipman, whose book Femme Fatale: Love, Lies and the Unknown Life of Mata Hari has just been released.