The FTC examined the possibility of unsubstantiated carbon offset programs that some U.S. companies offer to bolster their environmentally friendly reputations, which some critics call "greenwashing."

Corporations such as Dell and Volkswagon allow consumers to "purchase" carbon offsets for a variety of products.

Wednesday's New York Times said FTC Chairwoman Deborah Platt Majoras said there was "a heightened potential for deception" in the increased use of "greenwashing" campaigns, though the FTC hasn't revamped its environmental advertising guidelines since 1998.

The FTC inquiry doesn't target specific actions but some observers said the hearing suggested major corporations may face increased scrutiny as the practice becomes more prevalent.

"The carbon market is a leading example of the challenge of making sure that when people put their money into what they hope will improve their planet, that there is real follow-through," Daniel Etsy, director of the Center for Business and the Environment at Yale University, told the Times.