A group of 18 US states yesterday announced they are to sue the Bush administration in an attempt to force it to accelerate the development of legislation to curb greenhouse gas emissions from motor vehicles.

Last April, in a case brought against the Environmental Protection Agency (EPA) by the state of Massachusetts, the Supreme Court ruled the EPA has the authority to regulate emissions from new cars and trucks under the Clean Air Act, and said the reasons the EPA gave for declining to do so were insufficient.

However, since then the federal agency has not acted on the court's ruling, instead claiming it needs to undertake a public consultation before proposing fresh regulations. It has also consistently blocked attempts by individual states, led by California, to set their own regulations governing car emissions, arguing that the matter is a federal issue.

The EPA's inaction has infuriated the group of 18 states, including Massachusetts, California and New York, who are now accusing the EPA of deliberately "dragging its feet" on the issue.

In a petition filed yesterday, they claim that last year's Supreme Court ruling requires the EPA to decide whether to regulate emissions from vehicles and call upon the US Court of Appeals for the District of Columbia Circuit to require the EPA to act within 60 days.

"The EPA's failure to act in the face of these incontestable dangers is a shameful dereliction of duty," said Massachusetts attorney general Martha Coakley, the lead plaintiff.

Speaking to Associated Press, EPA spokesman Jonathan Shradar said the Supreme Court required the agency to evaluate how it would regulate greenhouse gas emissions from cars and other vehicles but set no deadline. He added that the evaluation would form part of a work to develop a broader regulatory framework that would cover emissions from all sources, not just motor vehicles.

"We want to set a good foundation to build a strong climate policy of potential regulation and laws we can work toward and actually see some success, " Shradar said.

Environmental groups accused the EPA of delaying tactics, arguing that it was in violation of the Supreme Court ruling.

David Hawkins, climate centre director for the Natural Resources Defense Council, said the EPA appeared committed to delaying any real action to reduce global warming pollution "for as long as possible and certainly until the next administration", while Friends of the Earth called for EPA administrator Stephen Johnson to resign over his continued "inaction on global warming a full year after the groundbreaking Supreme Court decision".