A US report ahead of British retailer Tesco's entry to the market has warned consumers of "significant gaps" between the retailer's promises and its actions.
Tesco, the world's third-largest retailer, has enjoyed a largely positive reaction in the United States.
Los Angeles-based Occidental College said in its report it believed Tesco would have a decisive impact on the US retail and that consumers needed to be aware of its record to pressure it to be an "agent for positive change."
Tesco's US rollout begins in November and it aims to open around 100 stores across in the four western US metropolitan areas of Los Angeles, San Diego, Phoenix and Las Vegas by next year. They will be called "Fresh & Easy Neighborhood Market."
"Tesco has been especially adept at marketing itself as a socially responsible corporation," said Robert Gottlieb, director of Occidental's Urban and Environmental Policy Institute.
"However, our examination of Tesco's policies shows that its track record has significant gaps between what it has promised and how it has achieved its current position as one of the top multinationals."
Tesco International Affairs spokesman Greg Sage played down the research and said such reports were "common in California." Tesco would be a good neighbour, a steward of the environment and treat its workers with respect, he said.
But Mr Gottlieb questioned whether Tesco's decision not to engage in talks with unions and take on only part-time workers, and to bring some British suppliers with it rather than focusing on locally sourced goods were at odds with its promises.
Tesco wants to set itself apart in the world's biggest consumer market by stressing its employment and environmental credentials. It has also promised to bring low-cost fresh food to poorer communities.