The US Senate has announced that it has decided against boosting mileage standards for sport utility vehicles (SUVs), and will continue to allow federal agencies to set fuel economy requirements.

The decision has arrived as part of a broad energy bill that the Senate is trying to finish this week before adjourning for its month-long August recess.

Under current law, the US passenger car fleet must average 27.5 miles per gallon (mpg). However, SUVs, mini-vans and other light trucks, which currently account for more than half of all new vehicles sold, are to be required to average 22.2 mpg by 2007.

The Senate rejected 65 to 32 a proposal by Richard Durbin, an Illinois Democrat, that would have required cars and SUVs to average 40 mpg by 2015.

'Detroit is falling further and further behind when it comes to new and responsible technology to deal with fuel efficiency and the environment,' said Senator Durbin. 'This energy bill before us doesn't challenge the automobile industry to do better.'

The decision has caused consternation amongst US environmental groups, who want a boost in fuel standards to slash gasoline use and reduce U.S. dependence on foreign oil imports.