The companies are accused of violating the Clean Air Act by failing to promptly notify the Environmental Protection Agency (EPA) about defects in air pollution controls installed on several 1998-2006 Mercedes cars.

The Justice Department and the EPA said the vehicles had faulty catalytic converters or air pumps that created an extra 500 tonnes of harmful pollutants such as nitrogen oxides and carbon monoxide.

"Reliable and effective automobile pollution control systems are essential to protect human health and the environment from harmful automobile emissions," said Sue Ellen Wooldridge, an assistant attorney general at the Justice Department.

"Mercedes' failure to alert EPA to a number of defects in emission-related components over a multi-year period is a serious violation because it deprived EPA of the opportunity to promptly determine whether emission standards would be exceeded and whether to order a recall of any of these vehicles," she said.

After the EPA began an investigation, Mercedes-Benz USA began voluntary recalls for two of the defects and extended warranty coverage to address a third defect, at an estimated total cost of about 59 million dollars.