A US federal appeals court on Friday unanimously upheld guidelines from the government's highway safety agency allowing automakers to limit some vehicle recalls by region.

According to The Associated Press, two consumer groups had challenged the National Highway Traffic Safety Administration's (NHTSA) policy that allows automakers to conduct recalls involving defects related to regional conditions such as snow or heat.

Public Citizen and the Centre for Auto Safety reportedly asserted that a 1998 letter sent by NHTSA to automakers offering guidelines on the regional recalls should be considered a rule change requiring public comment.

The consumer groups said it amounted to a "de facto regulation" and violated a federal law requiring that all vehicle owners be notified of a recall regardless of where they live or where the vehicle is registered.

The appeals court disagreed, AP said. Judge Harry Edwards of the US Court of Appeals for the District of Columbia Circuit wrote the "guidelines are nothing more than general policy statements with no legal force. They do not determine any rights or obligations, nor do they have any legal consequences," Edwards wrote.

In a concurring opinion, Judge Raymond Randolph said the policy guidelines do not constitute final action by the agency "because they do not impose any legal consequences on the regulated automakers."

According to AP, attorneys for the government had said one could not look at the 1998 letter and predict how the agency would proceed in individual cases. They said NHTSA uses its technical expertise, experience and judgment in each particular case.

Clarence Ditlow, executive director of the Centre for Auto Safety, told The Associated Press his organisation disagreed with the ruling. He said the guidelines were "for all practical purposes final action" from the agency.

The US District Court for the District of Columbia dismissed the group's lawsuit in 2004, leading to the appeal. The lower court said the letter was not a rule change but simply gave guidelines for regional recalls.

The court also said that regional recalls do not violate the Motor Vehicle Safety Act because the act does not say that recalls must be nationwide.

AP noted, however, that some states have objected to the practice. In November 2005, Wisconsin attorney general Peggy Lautenschlager asked the Department of Transportation to make recalls national. She cited a regional recall by General Motors in August 2005 that included bordering states Illinois and Michigan but excluded Wisconsin.