A group of conservationists across Colorado on Tuesday stepped up their criticism of Gov. John Hickenlooper for comments he made about oil and gas drilling spills.

Hickenlooper, the group said, misinformed the public when he told FOX31 recently, "There have been a few spills." The group includes the Sierra Club, Clean Water Action, Western Colorado Congress of Mesa County and Coalition for a Clean Colorado.

Oil and gas companies have reported hundreds of spills annually since 2000, said the conservationists, citing state Oil and Gas Conservation Commission figures. Environmentalists contend some of those spills have contaminated surface and ground water.

Hickenlooper's remarks follow comments he made in a Colorado Oil & Gas Association radio ad in which he says the state has "not had one instance of groundwater contamination associated with drilling and hydraulic fracturing" since the overhaul of the state's oil and gas protections in 2008.

Environmental groups called for Hickenlooper to pull the ad. The governor responded by apologizing, saying that his administration should have "reached out to the environmental community and asked if they were okay with the language."

Tisha Schuller, president of the Colorado Oil and Gas Association, has said neither drilling nor hydraulic fracturing has affected groundwater since the 2008 rules went into effect.