Following last week’s statements by White House budget chief Mick Mulvaney, regarding the “hierarchy” he established as a congressman to determine which lobbyists he treated favorably, Sen. Bernie Sanders (I-Vt.) and five Democratic lawmakers on Tuesday demanded a federal investigation into Mulvaney’s political activities.

Mulvaney’s remarks “reinforce the American public’s worst fears about a corrupt Washington establishment that sells access and is rigged for special interests with teams of lobbyists and deep pockets,” wrote the senators in a letter to the Office of the Special Counsel.

Speaking at a meeting of the American Bankers Association last week, Mulvaney, who is the interim head of the Consumer Financial Protection Bureau (CFPB) and well as running the Office of Management and Budget (OMB), told a crowd of financial executives, “We had a hierarchy in my office in Congress. If you’re a lobbyist who never gave us money, I didn’t talk to you. If you’re a lobbyist who gave us money, I might talk to you.”

The statement clearly implied that Mulvaney and other lawmakers who decide policies affecting big banks may be open to bribes, said critics including former Labor Secretary Robert Reich.