A ban on federal funding for gun violence research was criticized today by a group of four former U.S. surgeons general, including a President George W. Bush appointee.

These former public health leaders called on Congress to end the controversial 20-year-old ban, joining a growing number of doctors and elected officials who object to the 1996 federal budget amendment that essentially prohibits the Centers for Disease Control and Prevention from investigating shootings as a public health problem.

The ban, long a sore spot in the medical community, jumped into the national spotlight after the 2014 mass shooting at Sandy Hook Elementary in Newtown, Conn. President Obama ordered the CDC to get back to studying the causes of gun violence. But the agency didn't move because of the 1996 budget language that has been reauthorized every year by Congress.

“It is only through research that we can begin to address this menace to our nation’s public health,” wrote the three former surgeons general appointed by a Democrat, Regina Benjamin, Joycelyn Elders and David Satcher.

The lone appointee by a Republican, Richard Carmona, penned his own letter to Congress, with the same message. Carmona also noted that without appropriate research “we really have no idea what policies and/or regulation may be needed in order to ensure the public’s safety.”

The push by the former surgeons general was organized by Americans for Responsible Solutions, a political action committee that supports gun control and was created by Gabrielle Giffords, the former Arizona congresswoman who was seriously wounded in a 2011 mass shooting in Tucson.

Last year, a group of 110 Democratic U.S. representatives also made a public call for the resumption of federal funding.

Most major medical societies — including the American Academy of Pediatrics, American Medical Society and National Association of Medical Examiners — want the ban reversed.

Even the man who wrote the original 1996 amendment, former representative Jay Dickey (R-Ark.), has called on Congress to allow the CDC to study gun violence. He acknowledged that his amendment was a mistake.

But Congress has been unmoved.

Many Republican members, with the support of the National Rifle Association, accuse the CDC of wanting to use public health research to advocate for gun control.

Current Surgeon General Vivek Murthy has not publicly addressed the topic since he assumed his current position in December 2014, although he has described gun violence as a health epidemic.

Murthy's office did not immediately respond to a request for comment.