General Motors has been accused of using a Volkswagen-style defeat device in its heavy-duty diesel trucks in order to beat emissions tests and bypass pollution regulations.

According to Bloomberg, 705,000 owners of Silverado and Sierra HD trucks sold between 2011 and 2016 fitted with the 6.6-liter Duramax diesel engine filed a class-action lawsuit against the Detroit automaker claiming the company used multiple defeat devices to skirt emissions laws.

The suit alleges GM's defeat device allowed its trucks to pass regulatory inspections despite spitting out emissions two to five times the legal limit under regular driving conditions, a far cry from the VW diesels which were emitting up to 40 times the nitrogen oxide pollutants allowed in the US.

It's possible GM's HD trucks have been snared in a misinterpretation of the relationship between emission controls and diesel engines, where software is used to reduce emissions controls over a specific range of parameters such as the engine turning over at high revolutions due to increased speed or towing.

GM becomes the sixth automaker accused of cheating on diesel emissions since 2015, once again undermining the credibility of clean-diesel technology. Just this week the U.S. Justice Department decided to go after FCA for alleged violations of emissions laws, while German authorities raided 11 Daimler offices in search of potentially fraudulent emissions data.

In a statement the company said "These claims are baseless and we will vigorously defend ourselves. The Duramax Diesel Chevrolet Silverado and GMC Sierra comply with all U.S. EPA and CARB emissions regulations." Shares of GM fell by as much as 4 percent on the news.