PHILADELPHIA — A Democratic U.S. senator demanded Thursday that the National Rifle Association respond to charges it placed a paid spy in rival gun-control organizations for more than a decade.

The powerful firearms lobby has remained silent since reports broke last week that gun-control activist Mary McFate, 62, of Sarasota, Fla., was allegedly snooping on several of the nonviolence groups for the NRA.

Sen. Frank Lautenberg of New Jersey asked the NRA to confirm or deny the charge; reveal what she was paid, if anything; disclose the names of any other informants in the gun-control movement; and put a stop to the practice.

"Although the NRA and I have certainly had our disagreements over the years, I hope that we can agree that the gun violence prevention debate should be based upon an open and honest exchange of ideas, not on underhanded tactics," Lautenberg wrote in a letter faxed Thursday to NRA headquarters in Virginia.

The NRA has not been responding to the spying charges. Messages left with two prominent NRA board members — U.S. Sen. Larry Craig, R-Idaho, and the rock star-turned-radio host Ted Nugent — were not returned Thursday.

McFate, a former flight attendant and sex counselor, infiltrated an animal-rights group in the late 1980s at the request of U.S. Surgical, a medical research company.

A 1997 resume for Mary Lou Sapone, her married name, lists her as an "intelligence and investigations" consultant and a former senior investigator specializing in "covert operations" for a Connecticut consulting firm. The resume surfaced in legal papers related to a Maryland business dispute.

The resume lists her hobbies as hunting, trapping and fishing, shooting sports and "pugil stick fighting."