Actor Sylvester Stallone poses during a photocall for the movie "Bullet to the Head" by director Walter Hill at the Rome Film Festival November 14, 2012. (Reuters file photo)

Sylvester Stallone handed over millions of dollars to his late sister at the height of his fame after she blackmailed him and threatened to wreck his career.

Stallone's half-sibling, Toni-Ann Filiti, died of lung cancer last year at the age of 48 and it has now emerged her famous brother handed her a multi-million dollar sum in the 1980s and agreed to pay her a monthly income and set up a trust to cover her medical expenses.

A representative for Stallone has confirmed the payout and revealed the money was handed over after Filiti blackmailed the star with a series of false allegations of physical abuse.

The spokesperson tells New York Post gossip column Page Six, "Unfortunately, celebrities, politicians and athletes frequently find themselves the targets of blackmail efforts by family members and associates who fabricate claims in order to extort payments from them."

The Rocky star's mother Jackie has also opened up about the alleged blackmail plot, claiming Filiti was addicted to prescription drugs and the actor was trying to help her.

She says, "This was nothing more than a shakedown. Toni-Ann was on 65 Oxycontin pills a day, and she threatened Sylvester. A drug addict will do anything. When Sylvester became famous... He was trying to help her. He caved in... At the time (in 1987) he was very hot, and his lawyers said, 'Give her something just to shut her up.'"