NEW YORK (CNNMoney.com) - GM, which has trailed some of its competitors in offering fuel-efficient hybrid vehicles, is looking at a new version known as "plug-in hybrids" not yet on the market, which can offer drivers even better mileage, according to someone familiar with company plans.

Hybrid vehicles depend on both a gasoline-powered engine and an electric motor.

GM is working on developing a "plug-in" hybrid, which like its former EV1 electric car, would need to be recharged but could run on all electric power much of the time.

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While the batteries of current hybrid vehicles are charged by the gasoline engine as well as power retrieved through braking, a plug-in hybrid can also be charged by being plugged into an electrical outlet. That significantly lessens the need for gasoline power to charge the batteries.

GM spokesman Brian Corbett wouldn't comment on the company's product plans, but he said GM (Charts) is looking at a wide range of options for the future.

"We are always looking at ways to provide fuel efficiency to our customers, and energy independence to the United States," said Corbett. "Obviously, a plug-in hybrid is something that would definitely be on our radar screen, something we could consider for the future. But I'm not saying we're going to do one or the other."

GM has been offering hybrid versions of its full-size pickups, the Chevrolet Silverado and the GMC Sierra, since 2004, and it is due to roll out a hybrid version of the Saturn Vue crossover SUV this fall

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The company offered a limited production of an electric-only car, the EV1, for five years starting in 1996. But it was never more than a niche product, selling only 411 in 2000, the last year they were available.

The company has come under criticism from the environmental movement for not backing the product, with the automaker being portrayed as one of the major villains in a documentary, "Who killed the electric car?" The movie will open in limited release June 28, and is scheduled to be in most major markets by the end of August.

GM has also come under harsh attack from New York Times columnist Thomas Friedman, who called the automaker's product offerings and its incentives for buyers of large SUV's and pickups "dangerous to America's future."

GM officials respond that the company has more models that get 30 miles per gallon or better than any other automaker, and that it has sold 1.9 million vehicles that can run on either gasoline or on fuel that is 85-percent ethanol.

Corbett said GM's experience with the EV1 gives it an advantage over other automakers. But he said the experience with the EV1, which needed to be plugged in using a special docking mechanism in order to charge, shows the challenges any plug-in hybrid would face.

Corbett said GM would likely need to find a way to have a plug-in hybrid work with any standard electrical outlet to make it commercially viable. While a plug-in hybrid can work with just the gasoline engine, it needs to be plugged in to run most efficiently.

"A plug-in hybrid is going to require a change in consumer's daily routine," said Corbett. "If something is going to work, you have to make it as easy as possible for the consumer to adjust to a new form of vehicle propulsion. Whether it's our Saturn Vue Green Line, or the Chevy Tahoe which comes out in '07 or the Toyota Prius or Ford Escape, drivers of current hybrids don't have to do anything different."

GM has badly trailed competitors such as Toyota and Honda, as well as Ford, in its development and marketing of hybrid vehicles, and it's support for the product has been called soft by critics.

Robert Lutz, GM's vice chairman of product development, said at the Detroit auto show in 2004 that hybrids did not make economic sense for buyers or the automaker with gas then at $1.50 a gallon. He called them an "interesting curiosity."

A year later, with the Toyota Prius selling well, Lutz admitted that GM had made a mistake in its limited commitment to hybrids, saying they were important to the company's overall marketing and public relations efforts.

"It's not clear that you'll ever be able to recapture the cost of a hybrid in the pricing. But what we forgot in the equation was the emotional aspect of it," he said. "Whether the cars economically make sense or not, we cannot not be in that market."

Federal support for the development of plug-in hybrids was included in President Bush's speech April 25 laying out administration plans to combat rising gasoline prices. He vowed at that time to push for a $31 million increase in federal research and development support to speed up research into advanced battery technologies.

Related: How Detroit is learning to stop worrying and love hybrids