Senator Elizabeth Warren, the Massachusetts Democrat who has taken on Wall Street banks and the issue of income inequality, is now going after Mary Jo White, the chairwoman of the Securities and Exchange Commission.

In a 13-page letter to Ms. White on Tuesday, Ms. Warren called her two-year stewardship of the S.E.C. “extremely disappointing” and not in keeping with the kind of leadership that Ms. White had promised to deliver during her Senate confirmation hearing.

The senator said Ms. White had been slow to promulgate rules with regards to chief executive pay and failed to require companies settling enforcement actions to admit to wrongdoing. Ms. Warren also took issue with Ms. White having to recuse herself from too many matters her husband’s law firm has worked on and being too deferential when it came to giving Wall Street investment firms that had pleaded guilty to violating securities laws.