General Motors Corp. is not doing nearly enough to improve the fuel economy of its vehicles, according to a report released yesterday. That might not seem like news, but the organization that released the report, the Boston-based Coalition for Environmentally Responsible Economies, has been consulting with GM for almost 10 years and has been praised by the company in the past for being industry-savvy and reasonable in its expectations. The report notes that although GM has made some environmental progress by improving fuel efficiency in certain vehicles and reducing pollution at its factories, those gains have been offset by the rise in popularity of highly fuel-inefficient sport utility vehicles. The report comes at a time when the Bush administration and Congress are considering toughening the federal Corporate Average Fuel Economy standards.