A coalition of anti-abortion legislators is calling for an end to human embryonic stem cell research at the National Institutes of Health, reviving a debate on the ethical use of aborted fetal materials in research after nearly two decades of inaction on the controversy.

Rep. Chris Smith (R-NJ) and Sen. Roger Wicker (R-MS), along with 16 other House members and five other senators, sent a letter on Friday to NIH Director Dr. Jay Bhattacharya asking NIH to halt the use of embryonic stem cells and fetal cell lines obtained through abortion procedures and instead use new alternative methods that have been pioneered in recent years.