Commerce Department Secretary Wilbur Ross may have violated a criminal conflict of interest law by holding stock in companies that could have been affected by Trump administration actions in which he was involved, a campaign finance watchdog said in a complaint filed Monday.

The nonprofit Campaign Legal Center's complaint said public records suggest that the billionaire Ross also may have violated three laws "that prohibit certain false statements or omissions" in congressional testimony and financial disclosure filings he made regarding his holdings.

The center asked the Commerce Department's internal ethics watchdog, the Office of the Inspector General, to "conduct a thorough investigation of the matter addressed in this complaint" and to make public its findings.

A lawyer for Ross, who since November has faced scrutiny for his financial holdings, after CNBC published this story issued a statement, saying, "Secretary Ross has not violated any conflict of interest law or regulation. He has not participated personally and substantially in, nor taken any action in regard to a particular matter that would have had a direct and predictable effect on his financial investments."

CLC's 115-page complaint flags Ross' involvement in a Trump administration investigation into whether the United States should impose a tariff on steel imports at the same time he was holding stock in his former investment management firm, Invesco, which "had acquired a major interest in Chinese steel that the steel investigation directly and predictably affected."

The center also raised concerns about Ross' initial failure to disclose stock ownership in Greenbrier, "a steel-dependent rail car manufacturer," as well as his holdings in shipping giant Navigator while he was participating in the steel investigation and in the Trump administration's effort "to promote the natural gas trade." The steel probe and the natural-gas push affected Navigator's interests, the watchdog argued.

The group said Ross also may have retained other assets that represent a conflict of interest.

The center noted that Ross' public disclosure filings do not account for his divesting 46 assets that he had been required to shed, including interests in the Bank of Cyprus.

The group says there is doubt that Ross properly addressed conflicts stemming from 25 carried interests in private equity funds.

Finally, the complaint said Ross also may have made false statements or omissions in his recent congressional hearing, and in his Nov. 1 compliance certification, in which he said he had sold all interests in the companies in which he was required to divest: Air Lease, Invesco and Sun Bancorp.

The complaint said that a day before filing that certification, Ross obtained a new interest in Sun Bancorp, and later missed the deadline for disclosing this additional interest.

The center's ethics counsel, Delaney Marsco, scoffed at Ross's prior explanations for some of the situations highlighted by the complaint. Ross had claimed to have been unaware that he owned stock in the companies potentially affected by administration policies or inquiries after he said he was divested of such shares.

"Our analysis shows Ross participated in matters affecting his personal interests," Marsco said. "He has lots of excuses, but they don't add up."

"He can't be both the legendary investor who managed complex private equity funds and hapless official who doesn't even know what he owns," Marsco said.

The complaint comes a month after the U.S. Office of Government Ethics warned Ross that his action, which "included your continued ownership of assets required to be divested in your Ethics Agreement," and his opening of short sale positions "could have placed you to run afoul of the primary criminal conflict of interest law."

David Apol, the ethics office's acting director and general counsel, said in a letter to Ross in July that financial disclosure forms and compliance documents submitted by Ross "contained various omissions and inaccurate statements."

One the heels of that warning, Ross announced he would sell off all of his equity holdings and buy Treasury securities with the proceeds.

Full statement from a lawyer for Wilbur Ross: