Marilyn Monroe documentary claims to reveal identity of biological father

The identity of Marilyn Monroe's biological father is set to be revealed in a new documentary.

Titled Marilyn, Her Final Secret, the investigative project follows extensive DNA research to discover who the Hollywood icon's father really was, Variety reports.

This information was a secret even to the Gentlemen Prefer Blondes star throughout her life.

The documentary was directed by Francois Pomès and includes the work of French molecular archaeologist Ludovic Orlando.

Using a hair sample from renowned authenticator John Reznikoff and a saliva sample from the great-grandchild of Marilyn's suspected father, Charles Stanley Gifford, Ludovic pieces together the DNA evidence.

"The hair that we used from Monroe was collected by the person who embalmed her body the day she died and we were able to draw up 22 per cent of her genetic profile from that thanks to a DNA fragment found in the keratin," said Francois to the outlet.

The director added he "spent years and sleepless nights" working to break this "family secret".

"The thing that touched me the most was seeing the reaction of Gifford's family who were overwhelmed by this irrefutable evidence," he added.

The film is set to premiere on French channel Toute l'Histoire in June, with the rights also sold to other broadcasters around the world.

Monroe died at the age of 36 in 1962.