More than 20 organizations on Monday called on House Speaker Paul Ryan to end the congressional witch-hunt targeting Planned Parenthood, saying the effort is “setting a dangerous precedent for the ways in which Congress investigates individuals and organizations.”

The so-called Select Investigative Panel on Infant Lives, which has been roundly condemned by women’s health and civil liberties advocates as well as close to 180 House Democrats, was created to look into fetal tissue research in the wake of last summer’s video exposé by anti-abortion activists that purported to show Planned Parenthood officials admitting to selling fetal body parts.

“Such a standardless approach to congressional investigation harms those engaged in reproductive health work today, but tomorrow it could be environmentalists, free speech advocates, academicians, scientists, or indeed any group that happens to draw the ire of the majority.”

However, the ACLU-led letter says the panel’s Republican majority “has gone well beyond that scope and engaged in a fishing expedition in an apparent attempt to ratify a discredited smear campaign against Planned Parenthood and those associated with it.”