The director of the Office of Government Ethics said there is "strong reason to believe" that senior adviser Kellyanne Conway violated federal rules by endorsing Ivanka Trump's clothing line, urging the White House to investigate the matter and consider disciplining her.

In a Feb. 13 letter to White House Deputy Counsel Stefan Passantino, OGE Director Walter M. Shaub Jr. wrote that Conway's comments appeared to be "a clear violation" of federal ethics rules that bar federal employees from using their public office to endorse a product.

"Under the present circumstances, there is strong reason to believe that Ms. Conway has violated the Standards of Conduct and that disciplinary action is warranted," he wrote.

Shaub added that the ethics agency has not been notified whether the White House has disciplined Conway, even though press secretary Sean Spicer said she was "counseled" after she promoted Ivanka Trump's brand on Fox News.

White House officials, including Conway, did not immediately respond to requests for comment.

Rep. Elijah E. Cummings of Maryland, the ranking Democrat on the House Oversight Committee, called on President Trump heed the agency's advice.

"This was a textbook violation of federal ethics rules, and the president should follow the independent advice of the Office of Government Ethics to impose discipline on Ms. Conway," Cummings said in a statement.

The ethics agency does not have investigative powers or enforcement authority. But the letter from Shaub steps up the pressure on the White House Counsel's Office to disclose whether it took any action in response to Conway's remarks. Shaub asked Passantino for a response by Feb. 28.

The episode began Feb. 9, when Conway touted Ivanka Trump's "wonderful line" of clothing, shoes and accessories during an interview she gave Fox & Friends from the White House briefing room.

"I'm going to give a free commercial here," she added. "Go buy it today, everybody. You can find it online."

Shaub noted in his letter that Conway's remarks closely resembled a hypothetical example in the federal regulations of the kind of endorsement of a private product that federal employees are barred from making.

"Ms. Conway's actions track that example almost exactly," he wrote. "Therefore, I recommend that the White House investigate Ms. Conway's actions and consider taking disciplinary action against her."

Ethics experts said that violating the rule barring using one's public office for private gain can trigger a range of disciplinary actions, including a multiday suspension or loss of pay. U.S. Fish and Wildlife Service employees, for instance, face a five-day suspension or termination for such a violation.

However, OGE has little recourse if the White House declines to take any disciplinary actions, as Shaub noted in a separate letter to the House Oversight Committee. The ethics office can merely issue a "nonbinding" recommendation and inform the president if an agency is failing to discipline an employee.

"However, such notice would be ineffective in this case because any decision not to take disciplinary action will have been made by the President," Shaub added.

Government watchdog groups said that they have little expectation that Trump will levy any punishment, noting that Conway was following his example of publicly promoting private products. (The president and vice president are exempt from the regulations governing the use of public office for private gain.)

"Forgive us if we don't hold our breath," said Robert Weissman, president of the nonprofit Public Citizen.