By Anthony Boadle and Esteban Israel BRASILIA/SAO PAULO (Reuters) – A government plan to shield Brazil from alleged U.S. spying by forcing global Internet companies to store data on Brazilian users inside the country has run into mounting opposition in Congress, politicians said on Monday. The legislation was proposed by President Dilma Rousseff following revelations that the U.S. National Security Agency conducted surveillance on her emails and phone calls, along with those of average Brazilian citizens. Brazil's largest political party, which is a Rousseff ally, is not supporting the requirement, which has Internet companies up in arms. The measure was added to a bill drafted in 2011 aimed at protecting the civil rights and privacy of Internet users in Brazil that could be put to vote in the lower chamber of Congress as early as this week.