Winnie Mandela angry over Jennifer Hudson biopic
The film, which is to star Oscar-winning Jennifer Hudson, is based on Winnie Mandela: A Life, by Anne Marie du Preez Bezdrob.
Titled Winnie, the South African-made film is due to start shooting in May.
According to the Johannesburg's Star newspaper, Bowman Gilfillan, one of the country's leading law firms, is representing Mrs Mandela.
The newspaper said the law firm has sent a letter to the production company saying: "It is difficult to understand how a production bearing the name of an individual who has not been consulted at all could ever be appropriate or tell the full story of that individual life."
Next month, the film Invictus, which tells the story of Nelson Mandela's first term as South Africa's president and his role in the Rugby World Cup of 1995, will be released in UK cinemas.