An Italian actress once declared "the most beautiful woman in the world" has accused her toyboy former fiancé of marrying a lookalike pretending to be her in a bizarre bid to get his hands on her multi-million dollar estate.

Gina Lollobrigida, 85, is threatening to take her ex-partner, Spanish businessman Javier Rigau y Rafols, to court, alleging he married an imposter in a bid to steal her fortune when she dies.

"This vile person married me by proxy, without my knowledge and without my permission, in order to inherit my estate after my death," Gina told Italian media in a press conference yesterday.

"There will be international investigations because I want to shed light on this squalid affair and all the people involved."

Gina said Javier, who is 34 years younger than her, was able to commit the fraud because he had tricked her into granting him power of attorney when they were still a couple.

"A while ago he convinced me to give him my power of attorney," Gina said. "He needed it for some legal affairs. But instead I fear that he took advantage of the fact that I don't understand Spanish ...Who knows what he had me sign."

The fraudulent marriage allegedly took place in Spain in 2010 but Gina claims she only found out about this week when she came across the paperwork by chance.

"I found a document in which it seems that in November 2010 he became my husband, in Barcelona, in front of eight witnesses," she said.

Gina alleged Javier had a lookalike, a woman called Teresa, pretend to be her at the ceremony. The marriage reportedly went ahead, and Gina claims it is all a "wicked" bid to lay claim on her estate when she dies.

Gina was one of the biggest sex symbols of the 1950s and 1960s, starring opposite Frank Sinatra and Humphrey Bogart in films including The World's Most Beautiful Woman, Come September, Trapeze and Never So Few.

Gina and Javier met in Monte Carlo in 1984. They were a couple for 22 years and engaged for some of that time, but split up in 2006.