General Motors Corp., vilified by environmentalists for killing the electric car, is hoping to bring one back.

But the new electric won’t be an emissions-free vehicle.

The new car, to be unveiled as a prototype early next year, would use an onboard internal-combustion engine as a generator to produce electricity to extend the range of the vehicle’s rechargeable batteries.

The idea was greeted enthusiastically by Chris Paine, director of “Who Killed the Electric Car?” The recent documentary took GM to task for creating and then abandoning the EV1, the first production electric vehicle since the early 1900s.

“Bring it on,” he said, noting that he has not doubted GM’s ability to produce an environmentally friendly electric vehicle but has criticized its commitment to marketing one.

“I hope this one can get from concept to showrooms,” he said.

Some environmental activists also seemed intrigued by the idea, noting that although it is not a “pure” electric vehicle like the battery-powered EV1, a generator-driven hybrid electric car still would consume far less fuel than a vehicle that relied on a larger, thirstier gasoline or diesel engine for propulsion.

“We shouldn’t make ‘perfect’ the enemy of ‘good,'” Berkeley, Calif.-based vehicle policy director for the Natural Resources Defense Council, Roland Hwang, said. GM “apparently recognizes that it is falling behind in the race for a piece of the ‘green’ vehicle market … and needs something it can get out there and sell in substantial numbers.”

He remained skeptical, however, saying that GM “is fond of showing us things it never brings to market. The question is whether this will be just a prototype for public relations or a real effort.”

GM won’t talk openly about its new electric vehicle — first hinted at in an interview Vice Chairman Robert Lutz granted industry trade publication Automotive News this week.

But a source within the automaker’s technology division confirmed that GM had developed a prototype that would run initially on power provided by rechargeable lithium-ion batteries, switching to electricity provided by the on-board gasoline- or diesel-fueled generator when the battery charge is depleted.

The filmmaker, Mr. Paine, said he was in regular contact with GM engineers who support work on electric vehicles and had been told that the automaker planned to unveil the model in early January at the North American International Auto Show in Detroit.

The new car, if developed as a production model, would be recharged daily by owners and probably would deliver sufficient power from the batteries to cover the typical daily commute of 20 to 30 miles before depleting the battery charge and switching to electricity generated on-board.