French designer Coco Chanel spied for the Nazis during the German occupation of France in World War II, according to a new book.

Sleeping With The Enemy: Coco Chanel's Secret War, by Hal Vaughan, expands on long-standing evidence that the iconic designer had a double life and was the lover of a spy, Baron Hans Gunther von Dincklage.

"Sleeping With The Enemy pieces together how Coco Chanel became a German intelligence operative; how and why she was enlisted in a number of spy missions; how she escaped arrest in France after the war," New York publishers Knopf said in a statement.

Vaughan's book reveals not only was Chanel recruited to the Abwehr military intelligence organisation, but that von Dincklage was himself a "Nazi master spy."

He "ran a spy ring in the Mediterranean and in Paris and reported directly to Nazi propaganda minister Joseph Goebbels, right hand of Hitler."

Chanel was also "fiercely" anti-Semitic, the book says, although at the time she would not have stood out among numerous other high-profile compatriots later seen as having collaborated during the 1940-44 occupation.

Chanel - an orphan who became a revolutionary fashion designer - moved to Switzerland after the war before returning to Paris to take up her career in fashion.

She was never charged with any wrongdoing and died in 1971.