Toyota's green credo under fire in the US

Toyota is facing an attack on its image as one of the greenest car manufacturers from campaigners furious that it is opposing strict new fuel economy regulations under discussion in the US.

The Japanese company – whose hybrids, such as the Prius, have burnished its image for making more environment-friendly cars – has allied itself with the rest of the industry to lobby against the toughest new proposals being brought before lawmakers on Capitol Hill.

More than 8,150 messages of protest have been sent to Toyota as a result of a campaign by the Natural Resources Defense Council, a green group based in New York. "As the world's largest auto maker and inventor of the best-selling hybrid car on the market, Toyota has a responsibility to lead, follow or get out of the way as Congress debates the first substantial fuel-economy boost in decades," said Deron Lovaas, the NRDC's vehicles campaign director.

The protest emails and faxes urge Toyota to support a Senate energy bill that would set a 35 miles-per-gallon requirement on vehicles by 2020. Toyota and the "Big Three" US car makers – General Motors, Ford and Chrysler – are lobbying for a more modest 32 mpg by 2022, which they say is less likely to harm the industry while still generating a 40 per cent improvement in fuel economy standards.

A Toyota spokeswoman said: "For the first time, the industry has actually come together for a fuel economy increase, and everyone is pulling together in the same direction. Toyota is working very hard behind the scenes to achieve the best standards possible, not only for the whole industry but to meet the energy and environmental goals that we all share."

The Big Three have lost market share to Toyota in part because of the newcomer's reputation for fuel economy. The Japanese firm is poised to overtake General Motors as the world's biggest car manufacturer by production volume this year.