The inspector general for the National Labor Relations Board is investigating whether board member William Emanuel should have recused himself in a major decision that benefits employers.

Following the opening of the probe, Emanuel told lawmakers that he would be amending a letter he sent them in late December regarding whether he should have recused himself in a case in which the board, the federal government's main labor law enforcement agency, reversed its controversial joint employer policy.

"I have reviewed my responses to your questions that were forwarded to you be the NLRB's Office of Congressional Affairs on January 26th and believe they require further clarification. Accordingly, I will be providing you with a further response," Emanuel said in a Feb. 1 letter to Sens. Patty Murray, D-Wash., Elizabeth Warren, D-Mass., Margaret Hassan, D-N.H., and Reps. Bobby Scott, D-Va., Gregorio Sablan, D-N. Mariana Islands, and Rep. Donald Norcross, D-N.J.

The controversy involves a December case called Hy-Brand Industrial Contractors Ltd. and Brandt Construction Co. The board overturned its 2015 board decision in a case called Browning-Ferris Industries, reversing the board's controversial joint employer policy. Joint employer refers to when one business is so intertwined with a second one that it can be held legally responsible the second business's workplace policies. Until 2015, that required "direct control" of the policies. But after Brown-Ferris the board, then with a Democratic majority, changed it to the much vaguer "indirect control," a potentially vast expansion of corporate legal liability, especially for businesses that franchise. In Hy-Brand, the now GOP-majority board returned the requirement back to direct control.

Following the new board vote, Democrats demanded to know if Emanuel had recused himself in the case. "Given that your former partners at Littler Mendelson PC represented a party in [the Browning-Ferris case] before the board, did you recuse yourself from the board’s decision to move to remand the [Browning] case from the U.S. Court of Appeals for the D.C. Circuit back to the board? If not, why not?" the lawmakers asked.

In response, Emanuel confirmed he voted in the case and defended his decision. He said had not been aware that his former law firm had represented Leadpoint Business Services, a party in the Browning-Ferris case — "Littler Mendelson is a huge law firm of more than 1,000 lawyers," he noted — but the connection was too remote to merit recusal. "Littler did not represent Leadpoint in the BFI case before the D.C. Circuit, the board did not have jurisdiction over the case, and I was unaware that Littler had ever represented any party when the case was before the board," he said. Emanuel's Thursday letter said he would change that response.

Emanuel earlier had written to Warren and pledged to recuse himself from "all board cases" involving his former firm or its clients for "two years following my appointment to the NLRB.” The list included 162 former clients of Emanuel's or clients of Littler. Leadpoint Business Services was not on the list, however.

ProPublica reported Thursday that the NLRB Inspector General's office had started an inquiry into whether Emanuel violated ethics rules by not recusing himself. The board and the Inspector General's Office declined to comment.

The five-member board has only four members following the December retirement of Philip Miscimarra, its former chairman, and is split evenly 2-2 between Republican and Democratic members. In cases for which Emanuel would recuse himself, the board, which operates by simple majority, would then be 2-1 Democratic. President Trump has yet to nominate a replacement for Miscimarra.