For years, the Fed faced criticism that it wasn't being aggressive enough in raising rates. Now that it has started to hike, the central bank is under increasing fire for moving too soon.
The latest scrutiny comes from Joachim Fels, global economic advisor at Fed bond giant Pimco, who said the Fed shouldn't be tightening policy with the evidence so clear that it is falling well short of its inflation mandate.
Fels' argument: Much like the position that waiting so long to raise rates would give the Fed little ammunition to use against a downturn, hiking now will keep inflation too low and possibly itself lead to another slowdown or recession.
Fed officials have said they believe the economy is sufficiently strong to handle rate increases and presents the opportunity to start normalizing policy after years of historically accommodative actions.
"The prize of opportunistic tightening comes at a price: By hiking rates and starting balance-sheet runoff when inflation keeps undershooting, the Fed risks cementing inflation expectations firmly below target," Fels wrote in a blog post for Pimco.
"Some argue that this is a price worth paying. After all, does it really matter whether inflation is running at 2 percent or 1.5 percent or 1 percent?" he added. "Well, the difference doesn't really matter until it does."