Building upon her recent role as the go-to inquisitor for Senate Democrats and a progressive bulwark as the White House changes hands, Sen. Elizabeth Warren (D-Mass.) is upping the ante for her criticisms of Securities and Exchange Commission Chair Mary Jo White. The latest salvo: a letter to President Barack Obama demanding that he fire her.

The letter, dated Oct. 14, focuses, once again, on a proposed rule that would require companies to disclose political payments. White has said her Commission has no plans, at least in the near future, to pursue the rule, citing a backlog of more pressing work on its agenda and budgetary restrictions Republicans successfully added to an omnibus spending bill, a rider that specifically restricted the use of funds needed to issuing a final rule requiring public companies to disclose these political contributions.

“This brazen conduct is merely the most recent and prominent example of Chair White undermining your Administration's priorities and ignoring the SEC' s core mission of investor protection,” Warren wrote. “From the beginning of her tenure, Chair White has made clear that she is concerned that companies disclose too much to investors—a presumption directly counter both to the views of investors themselves and the animating purpose of this agency for more than 80 years.”

The SEC’s ongoing disclosure effectiveness review is also fueling Warren’s discontent. She described it as a “curious presumption that public companies currently disclose too much information.”

White, she wrote, “has failed to complete disclosure mandates Congress enacted in the wake of the 2008 financial meltdown, while simultaneously devoting the SEC's limited discretionary resources to a far-reaching, anti-disclosure initiative cooked up by big business lobbyists seeking to reduce the amount of information public companies must make available to their investors.”

“She has remained conspicuously silent when your Administration has issued veto threats against anti-disclosure bills, providing cover to those in Congress who seek to roll back disclosure requirements and compromise the transparency and safety of our markets,” she added. “Enough is enough. To address your concerns on political spending disclosure, and to advance other priorities of your administration and investors, I respectfully urge you to exercise your unilateral authority…to immediately designate another SEC commissioner as chair of the agency.”

While demoting an existing Chair and selecting another from among the agency's current Commissioners would be an uncommon act, White's “extraordinary, ongoing efforts to undermine the agency's central mission make such a step necessary,” Warren added. “The only way to return the SEC to its intended purpose is to change its leadership.”