Winslet has already won two Golden Globes
Oscar organisers have dismissed a list claiming to reveal all those poised for Academy Awards as a "complete fraud".
The document, circulating on the internet, names Kate Winslet as best actress for her role in The Reader.
The list, which features an authentic-looking letterhead, also claims British film Slumdog Millionaire will bag the best picture and best director prizes.
Academy spokeswoman Leslie Unger said it was a forgery and the event's auditors were still counting votes.
"The document is a complete fraud," she said.
"There are only two people there who will know the complete list of winners in advance of the envelopes being opened during the ceremony."
Reports say the document appears to carry the signature of Sid Ganis, president of the Academy of Motion Picture Arts and Sciences, which presents the Oscars.
Ms Unger added: "The Academy's president is not advised of the winners in advance and no such list is created."
The document also names Mickey Rourke as best actor for his role in The Wrestler and the late Heath Ledger as best supporting actor for The Dark Knight.
Best supporting actress is named as Amy Adams for Doubt and the list also claims In Bruges will get the best original screenplay award.
It is not the first time this awards season that there have been rumours regarding supposed winners.
Golden Globe organisers were forced to apologise last month for a blunder on the awards website which suggested Anne Hathaway had won a best actress gong for Rachel Getting Married.
An asterisk had appeared by mistake on the site next to Hathaway's name in a list of nominees, sparking a flurry of reports that she would receive the award.
Winslet, who went on to win ahead of Hathaway, has been nominated for an Oscar on five previous occasions, but has yet to take home an Academy statuette.
However, she remains the favourite for the award following her double win at the Golden Globes and success at the Critics' Choice Awards.
As she attended a flurry of pre-Oscar parties, the actress told the BBC News website she was "permanently anxious" but "very excited" about the ceremony on Sunday.