The watchdog group Public Citizen is saying that as early as 2002, the Food and Drug Administration realized that people taking Avandia, GlaxoSmithKline’s popular diabetes drug, were at a serious risk of heart attack. FDA staff scientists then were saying that Avandia’s label should contain a reference to the chance of congestive heart failure.

This information was released by Public Citizen one day after a team of researchers led by Dr. Steven Nissen reported in the New England Journal of Medicine that people taking Avandia are at a 64% greater risk of dying of heart-related problems and a 43% greater risk of suffering a heart attack. GSK has sought to refute the NEJM study results, defending the drug’s safety and effectiveness in the treatment of type 2 diabetics.

At that point five years ago, the FDA chose not to alter the Avandia label or issue a recall. It conceded the existence of a higher heart risk but claimed that more research was needed. The agency said that some studies had contradictory findings, which is true even now.

Dr. Sidney Wolfe, the head of Public Citizen’s Health Research Group, criticized Avandia for some time now, including it in his annual “Best Pills, Worst Pills” list—in the latter category. In his view, the 2002 memo showed that the agency had disregarded its staff scientists’ concerns.

He issued a statement, part of which read, “As a result, millions of people—to the detriment of their health—are prescribed drugs whose risks are dangerously understated, instead of being prescribed safer, equally or more effective alternative drugs.” Dr. Wolfe also urged FDA Commissioner Andrew von Eschenbach to impose a “black-box” warning on Avandia or to ban it completely.