A high-ranking banking regulator was asked Friday by a pair of Democrats to answer questions about an alleged conflict of interest.

Sen. Elizabeth Warren (D-Mass.) and ranking member of the House Oversight Committee Elijah Cummings (D-Md.) demanded that Commodities Futures Trading Commission official J. Christopher Giancarlo be forthright about a transaction he conducted in September, months after being confirmed to his position.

The pair of lawmakers queried Giancarlo about why he rapidly sold stock in GFI Group, Inc.–a financial services company he had previously worked for–in a move that deviated from his previously disclosed plan to divest from the company in 15-day intervals.

Warren and Cummings also prodded Giancarlo to reveal why he hasn’t recused himself from matters involving two firms that bid-up the price of GFI stock last year, between July 25 and Sept. 12. Those outfits, CME Group, Inc., and BGE Partners, were both vying to acquire GFI (on Friday morning, BGE won the battle).

“The increase in the price of GFI stock appears to have netted you more than $100,000 in additional profits above the amount you would have made had the stock been sold prior to the price escalation,” Warren and Cummings said, citing Giancarlo’s personal financial disclosure.

The discrepancy between Giancarlo’s plan and the execution of the transactions, which the CFTC commissioner described as resulting from “a mistake in the design of the trading plan,” was first reported in late January by Bloomberg’s Robert Schmidt.

Warren and Cummings are calling on Giancarlo to remove doubts about his position by providing them with: copies of his CFTC ethics agreement and any amendments to it; official executive branch guidance on conflicts of interest “arising from your prior employment”; an explanation about how “mistakes” were made in formulating his initial divestment plan; how he will handle matters related to CME Group and BGE Partners; how he will avoid even future appearances of conflicts of interest, and documents that detail his severance package with GFI.

The issue of severance deals and the revolving door briefly became a topic of debate in President Obama’s second term. In 2013, during his confirmation process, it was revealed that now-Secretary of Treasury Jack Lew was, in 2009, given an almost $1 million bonus for taking a “full time high level position with the US government or regulatory body.”

Sen. Bernie Sanders (I-Vt.) voted against Lew’s confirmation, citing his exit deal, his many ties to Citigroup and, above all, his favorable views of deregulation. Warren supported Lew’s nomination.

In late January, Giancarlo also made headlines in the financial press for opposing post-2008 CFTC regulations, which, he claims, according to Bloomberg, “have shifted business overseas, made it more expensive to operate exchanges and will encourage high-speed trading that could have an unpredictable market impact.”

“Governments and regulators should not pick winners and losers in the commercial economy,” the only current Republican among four commissioners said. “Regulators should not substitute their judgment for the business judgment of commercial entities and participants.”

In their letter to Giancarlo, Warren and Cummings described the CFTC as “playing an increasingly important role in regulating over-the-counter derivatives.”

Derivatives trades involving credit default swaps featured heavily in the 2008 financial meltdown and the historic multi-billion dollar bailout of AIG.

Friday’s letter marks the second time this month Warren and Cummings have joined up to ask for more information from regulators. On Feb. 5, as The Sentinel noted, the pair asked the Federal Reserve to brief congressional staffers on a September 2012 leak of market-moving information.