An upcoming sequel to Oscar-winning movie Raging Bull has been thrown into jeopardy after bosses behind the original film filed a lawsuit in a bid to stop production. Executives at MGM, the studio behind the 1980 classic, are suing the producers of Raging Bull II and Jake LaMotta, the boxer whose life story was the basis for the first film, which starred Robert De Niro. The lawsuit, filed on Tuesday, alleges LaMotta, 91, should have offered MGM the rights to his 1986 sequel book first and the studio bosses fear the follow-up will tarnish the reputation of the original.