Arnold Schwarzenegger suspects his former rival Sylvester Stallone of having led a secret 1980s campaign to give the "Terminator" star a reputation as a Nazi sympathiser, according to a new book.

In "Fantastic: The Life Of Arnold Schwarzenegger", biographer Laurence Leamer claims Stallone told British journalist Wendy Leigh that Schwarzenegger's Austrian father helped round up Jews during the holocaust and the star-politician was a "secret admirer of Hitler", reports the Internet Media Database.

The two Hollywood action stars were bitter enemies in 1988, after the now California governor enjoyed an affair with Stallone's ex-wife Brigitte Nielsen.

In the book, Leigh claims Stallone paid her legal fees and covered her settlement to the Austrian actor after he sued her for libel when she published Stallone's alleged comments.

Although Stallone insists he did not contribute to Leigh's controversial tome, Leamer claims Schwarzenegger "reluctantly" confirmed he still believes Stallone worked to smear him as a fascist sympathiser. The pair have since settled their differences and are firm friends again.