President Donald Trump’s pick to be the next labor secretary, Andrew Puzder, has “serious conflicts of interest” due to his work for an industry lobby that sued to stop overtime reforms, Senate Democrats said Thursday.

In a letter sent to the nominee and obtained by The Huffington Post, Sen. Patty Murray (D-Wash.) told Puzder that the committee overseeing his nomination still had not received his ethics paperwork, and that she expected a “detailed account” of what steps he’d take to avoid conflicts related to overtime regulation.

“If you are confirmed,” wrote Murray, ranking member of the Senate Committee on Health, Education, Labor and Pensions, “your participation in any decisions, meetings, or conversations regarding the overtime litigation may put you in violation of legal ethics restrictions and prohibitions against conflicts of interest, raising questions about your ability to manage a key part of the responsibilities of the Secretary of Labor.”

Puzder is the chief executive of CKE Restaurants, which owns the Hardee’s and Carl’s Jr. burger chains. Until recently, he served on the board of the International Franchise Association, an industry group that has opposed workplace regulations pursued by the Obama administration. After former President Barack Obama reformed overtime rules to make them more generous to workers, the IFA joined other groups in suing to stop those rules from going into effect. So far, they have been successful.

According to the IFA, Puzder stepped down from the board earlier this month, weeks after Trump nominated him to be the next labor secretary. According to the most recent tax filings available, Puzder’s work for the nonprofit was unpaid.

Nothing about having served on IFA’s board should forbid Puzder from becoming labor secretary. But having been a board member of a lobby that sued to stop the overtime changes, Puzder showed a vested interest in whether the reforms survive, said Jordan Libowitz, a spokesman for Citizens for Responsibility and Ethics in Washington, a nonprofit ethics watchdog.