WASHINGTON (Reuters) - The White House should consider disciplinary action against presidential adviser Kellyanne Conway for appearing to violate government ethics rules by publicly endorsing Ivanka Trump products, the Office of Government Ethics wrote in a letter made public on Tuesday.

Counselor to the President Kellyanne Conway speaks at the annual March for Life rally in Washington, DC, U.S. January 27, 2017. REUTERS/Yuri Gripas

The letter, dated Monday and addressed to a White House ethics official, asked President Donald Trump’s administration to investigate the incident and gave it two weeks to provide its findings and detail any disciplinary steps taken.

Conway, Trump’s presidential campaign manager and now a senior counselor, said on Fox News last week that Americans should “go buy Ivanka’s stuff.” She spoke after retailer Nordstrom announced it was dropping the branded line of Ivanka Trump, the president’s older daughter.

Federal ethics rules prohibit executive branch employees from using their positions to endorse products.

“There is strong reason to believe that Ms. Conway has violated the Standards of Conduct and that disciplinary action is warranted,” Office of Government Ethics Director Walter Shaub wrote in the letter.

Stefan Passantino, the White House ethics official named in the letter, declined to comment. A White House spokesman did not reply to a request for comment.

The ethics office has little enforcement power. It can formally recommend disciplinary action if the White House does not act, Shaub said in a separate letter to two U.S. lawmakers who sought a review of Conway’s remarks.

That recommendation would not be binding, and the process would take until late April or early May, Shaub said. If the ethics office does formally recommend discipline, it would be up to the White House to decide any steps against Conway.

Norman Eisen, who was ethics chief under President Barack Obama, said Congress also could call hearings or subpoena documents if the White House did not act.

Trump himself earlier attacked Nordstrom for dropping his daughter’s brand. The ethics rules that bar endorsements do not apply to the president, though critics said his comments were inappropriate.

Nordstrom said it made the decision because sales had steadily declined, especially in the last half of 2016, to where carrying the line “didn’t make good business sense.”

In his letter to the White House, Shaub wrote that his office’s regulatory guidelines include an example violation in which a hypothetical presidential appointee promotes a product in a television commercial. He said Conway’s remarks closely mirrored that example of what not to do.

White House spokesman Sean Spicer said on Thursday that Conway had been “counseled,” but Shaub wrote that the Office of Government Ethics had not been informed of any corrective steps.