The activists claimed that this tape, and several others including discussions inside of medical facilities, revealed that Planned Parenthood was engaged in the illegal sale of body parts — a charge the organization firmly denied and that has not been supported in numerous congressional and state investigations that were triggered by release of the videos.

Planned Parenthood apologized for the tone of the doctor’s comments in that initial tape, but said that it and others were edited in a misleading manner. It said that a handful of its centers across the country had engaged in the legal transfer of fetal tissue, with permission of the women involved, for medical research.

But the videotapes and the allegations of illegal activity gave a powerful new force to the campaign to deny public funds to Planned Parenthood and led to increased vandalism, harassment and threats of violence against its clinics. The gunman in Colorado Springs who killed three and injured nine at a health center in November reportedly said “no more baby parts” to investigators, an apparent reference to the allegations.

In a written statement Thursday, the Center for Medical Progress called the lawsuit “frivolous” and accused Planned Parenthood of filing it “in retaliation for CMP’s First Amendment investigative journalism that has done nothing more than tell the truth about Planned Parenthood’s lawless operations.”

The 65-page suit states that the defendants set up a fake company called Biomax Procurement Services, and claimed to be part of a legitimate provider of fetal tissue to researchers. With fake identities, the suit charged, the defendants gained access to closed meetings of Planned Parenthood and the National Abortion Federation, then violated signed nondisclosure agreements as they wore hidden cameras and recorded hundreds of hours of conversations.