Christopher Reeve, the Superman star considered one of Hollywood's foremost family men, had a passionate affair with gay porn star Cal Culver, claims a new book.

Both Reeve and Culver have long been dead - Culver died of Aids in 1987 while the Hollywood heart-throb died in 2004 of heart failure, but the new claims have grabbed headlines.

In Hollywood Babylon Strikes Again, Culver gives details of their relationship in an interview conducted before his death, reported Daily Mail online.

The porn star alleges he met Reeve when they were auditioning for a Broadway role in the late 1970s.

"Christopher was a great lover and I think I liberated him sexually. I didn't think he was gay but he seemed willing to try anything once. He was curious," says Culver.

The news may surprise millions of Reeve fans who saw the star enjoy a healthy 12-year marriage to wife Dana.

He had a son William with Dana, as well as children Matthew and Alexandra from a previous relationship.

While Reeve is perhaps best known for his role as the macho superhero Superman, he also took on a role in 1982 film Deathtrap, which saw him share a kiss with co-star Michael Caine.

Reeve died in 2004, nearly a decade after he was paralysed in a horse riding accident.

Reeve was paralysed from the shoulders down when he fell from a horse in 1995. The accident turned him into a worldwide advocate for spinal cord research.