Sen. Robert Byrd (D-W.Va.), the longest-serving Democratic senator, is criticizing President Obama’s appointment of White House “czars” to oversee federal policy, saying these executive positions amount to a power grab by the executive branch.

In a letter to Obama on Wednesday, Byrd complained about Obama’s decision to create White House offices on health reform, urban affairs policy, and energy and climate change. Byrd said such positions “can threaten the Constitutional system of checks and balances. At the worst, White House staff have taken direction and control of programmatic areas that are the statutory responsibility of Senate-confirmed officials.”