President Donald Trump's nominee to become secretary of Labor, Eugene Scalia, earned more than $6 million working as a partner at the corporate law firm Gibson, Dunn & Crutcher, he reported in a financial disclosure form filed on Friday.

Scalia, son of the late Supreme Court Justice Antonin Scalia, said in the filing that he performed legal work for a range of the nation's largest financial institutions, Juul Labs, Facebook, Chevron, the Chamber of Commerce and the American Petroleum Institute.

Scalia also did legal work for insurance companies UnitedHealth Group and Allianz, investment bank Goldman Sachs, Ford Motor Company, Walmart, Wynn Las Vegas, Moody's, CVS, Delta Air Lines and transport firms CSX and Union Pacific. The form required Scalia to list sources of compensation exceeding $5,000 in a year.

In an accompanying letter, Scalia wrote to the Labor Department's ethics program manager that he will not participate "personally and substantially in any particular matter in which I know that I have a financial interest" unless he first obtains a waiver.

Upon confirmation by the Senate, he wrote, he will resign his position at Gibson, Dunn & Crutcher.

The Labor Department oversees U.S. labor laws and works to protect American workers. In an email, a representative for Citizens for Responsibility and Ethics in Washington, a good-government group that has been vocal about ethical violations in the Trump administration, said "on a first read, nothing really jumped out to us."

Scalia's work for big business is expected to exclude him from participation in some department matters likely to shape the rules that apply to businesses should he be confirmed.

For instance, Scalia is likely to recuse himself from the Trump administration's work to come up with a new version of the so-called "fiduciary rule" put in place under President Barack Obama, which was loathed by business groups and required financial advisors to act in their clients' best interests. The rule died in court, but officials have said they are working on a new version.

The Wall Street Journal, citing people familiar with the matter, reported earlier this month that Scalia would not be involved in that work.

Trump officially announced his intention to nominate Scalia to lead the Labor Department on Tuesday after first announcing the selection in a tweet in July. Alex Acosta, the previous Labor secretary, resigned amid scrutiny of the nonprosecution agreement he reached with convicted sex offender Jeffrey Epstein nearly a decade ago. Epstein died in jail in August in an apparent suicide while awaiting trial on new charges.

The acting secretary of Labor is Patrick Pizzella, who has come under scrutiny for his past work with disgraced lobbyist Jack Abramoff.