Slow sales have led GM to conclude that the next-gen models are not worth the required investment.

General Motors has permanently stopped the development of its next-generation hybrid pickup trucks and SUVs, a new report indicates.

Launched in 2004, the hybrid variants of Chevrolet's Silverado/Tahoe and GMC's Yukon/Sierra have been selling poorly in the United States. The low demand from customers has led GM to conclude that the next-gen models are not worth the large sum of cash that is needed to bring them to production.

Citing several anonymous but reliable sources inside and outside of GM, website GM Inside News reports that the exception to the rule might be the next-gen Cadillac Escalade, scheduled to hit showrooms in January of 2014 at the very earliest.

GM expects that the luxury SUV will be immensely popular among celebrities so offering a hybrid version of it is likely to generate positive publicity for the Cadillac brand. If it is given the green light for production, the Escalade Hybrid will be the only full-size GM SUV with a hybrid drivetrain.

Precisely what drivetrain will lurk under the Escalade's chrome-adorned body remains a mystery. If the rumors are true, the program that GM just shut down was putting the final touches on a revamped version of its current two-mode hybrid system. It was said to use more capable electric motors, an upgraded lithium-ion battery and boast more than two driving modes.

GM has not confirmed or denied the report. The next generation of Chevrolet and GMC's full-size pickups and SUVs are expected to be launched in less than a year so more details will be available soon.