A watchdog group has asked for a government investigation of whether Commerce Secretary Wilbur Ross made a “false statement” to the Office of Government Ethics about his stock holdings and violated insider trading rules when he engaged in a short sale of a shipping company with links to Russia.

Citizens for Responsibility and Ethics in Washington (CREW) sent a letter to Deputy Attorney General Rod J. Rosenstein and Acting Director of the Office of Government Ethics David J. Apol to investigate whether Ross made a false statement about divesting himself of his stock in Invesco, the firm he managed before taking office in the Trump administration.

The group’s executive director Noah Bookbinder and chair Norm Eisen also asked for an investigation of Ross’s sale of his shares in Navigator Holdings, the shipping firm, in October 2017. That company did business with a Russian energy firm whose directors included a Russian oligarch who was subject to U.S. sanctions and a son-in-law of Russian President Vladi­mir Putin.

By Ross’s own account, he used a short sale — a technique that rewards investors betting a stock will go down in price. Ross said the goal was to quickly reduce his position in Navigator, but the move had come after he learned journalists were working on articles about his holdings.

“Secretary Ross’s actions reflect an apparently knowing and repeated disregard for his ethics obligations,” CREW said in its letter.

An earlier letter by CREW to the Office of Government Ethics prompted the office to refer a matter to the Justice Department. In that letter, CREW asked for an investigation into whether President Trump had failed to disclose a liability to Michael Cohen for payments Cohen made to adult-film actress Stormy Daniels.

“This is a very serious matter,” Eisen said in an interview. “It’s even more worrying because it comes on the heels of a litany of other ethics questions and because it’s part of the larger ethics crisis afflicting this administration from the president on down.”

Separately, Sen. Ron Wyden (D-Ore.), the top minority-party member of the Senate Finance Committee, sent a letter to Ross asking him to reply to questions about who else knew about his short sales, whether he had personally executed them and how much profit he made on those transactions.

In its letter, the watchdog group said that Ross “appears to have traded on nonpublic information by engaging in a short sale of Navigator after learning of a forthcoming negative news story regarding the company.”

Ross has vigorously denied making false statements to the ethics office or of engaging in insider trading, calling such suggestions “unfounded allegations.”

CREW noted that Ross, who was confirmed Feb. 27, 2017, had deadlines May 28 and Sept. 25 to sell all his shares and restricted shares in Invesco. Yet Ross filed statements with the Office of Government Ethics Nov. 1 saying he had completed the sales. And on Dec. 21, he filed another statement reporting the sale of two more tranches worth $5 million and $25 million.

Ross has said he had been unaware of the final holdings.

The purpose of the divestitures is to make sure that a public official does not have a conflict of interest. Given Ross’s role in trade negotiations, some ethics and lawmakers have questioned whether the Commerce secretary had a conflict of interest from those shareholdings as well as investments now controlled by his family.

According to articles in Forbes, Ross also opened a short position in Navigator after learning that the International Consortium of Investigative Journalists and the New York Times were working on potentially negative articles about Ross and the company. The transaction was valued between $100,000 and $250,000. The stock dropped about 4 percent before Ross closed his position on Nov. 16, 11 days articles were published by The Times and the ICIJ.

In a statement Tuesday evening, Ross said that he was trying to speed up the divestment of Navigator stock and that some Navigator shares were in “electronic form” and could not be sold until they were transferred from an account managed by a trust agent to a brokerage account Ross himself could use.

Unlike shares he had purchased, these shares had been granted to him when Ross was a Navigator board member from 2012 to 2014 and were in the trust account.

Ross said that securities laws say that any information in the hands of news organizations is considered “by definition public information.” Moreover, he said, “The fact that the reporter planned to do a story on me certainly is not market moving information.”

However, legal experts note that news organizations can possess information considered nonpublic. In one notable case in the mid-1980s, Wall Street Journal’s Heard on the Street columnist Foster Winans leaked information to a pair of investors ahead of publication, giving them time to trade ahead of movements in the stock price. Winans was convicted of insider trading and mail fraud and served nine months in prison.