Lt. Gov. Jim Cawley on Thursday took a veiled swipe at Attorney General Kathleen Kane for criminally prosecuting an ExxonMobil subsidiary that had already agreed to pay a fine related to a 2010 Marcellus Shale wastewater spill.

At a natural gas industry conference in Philadelphia, Gov. Corbett's lieutenant questioned the "basic fairness" of disciplining a drilling company twice for the same accident.

In an address at the Shale Insight conference, Cawley touted the Corbett administration's record regulating the shale gas industry.

"While strict accountability must be the watchwords for this industry, responsible oversight and basic fairness require that no one should be punished more than once for the same mistake," Cawley said.

Cawley did not name Kane or the company, XTO Energy, but the references were clearly understood by the audience of more than 1,000, which broke into applause.

The attorney general's announcement Sept. 10 of charges against XTO struck a nerve with the industry.

XTO agreed in July to settle civil charges with the U.S. Justice Department by paying a $100,000 fine and spending about $20 million to upgrade its wastewater-management practices, an agreement federal officials called a model for the industry.

The company maintains the leak of toxic wastewater at a drilling site was an accident caused by a contractor. It promised to challenge the criminal charges "as unwarranted and legally baseless."

The issue has political overtones: Antidrilling activists have lauded Kane, a Democrat, for taking a hard line on an industry they believe has gotten soft treatment from the Republican Corbett administration.

Kane's spokesman, Joe Peters, said in an interview last week that going easy on environmental violators was unfair to law-abiding companies.

"This case sends a message that it is unfair to those companies large and small that do the right thing and follow the law to look the other way or diminish what other companies are doing or not doing," he said.

He also said Kane was "pro-business."

"You can be pro-business and people can prosper and at the same time be vigilant and keep the environment clean," he said.

Not many people at the conference interpreted the charges as positive.

"I'm certain the rest of the industry is going to look at this and say they're a little concerned," said Marty Durbin of America's Natural Gas Alliance, an industry advocacy group.