WASHINGTON — The White House on Thursday “counseled” Kellyanne Conway, one of President Trump’s top advisers, in an unusual show of displeasure after she urged consumers to buy fashion products marketed by Ivanka Trump, the president’s daughter. Legal experts said Ms. Conway might have violated a federal ethics rule against endorsing products or promoting an associate’s financial interests.

“Go buy Ivanka’s stuff is what I would say,” Ms. Conway said in a Thursday morning interview with Fox News, speaking from the White House briefing room. “I’m going to give a free commercial here: Go buy it today, everybody; you can find it online.”

Sean Spicer, the president’s press secretary, would not elaborate on what the counseling entailed.

Jason Chaffetz, the Republican chairman of the House Oversight Committee, said Ms. Conway’s comments were “wrong, wrong, wrong, and there’s no excuse for it.” Mr. Chaffetz — who so far had not acted on calls since Election Day to investigate ethics issues related to Mr. Trump — and the panel’s ranking Democrat, Elijah Cummings, formally asked the Office of Government Ethics for an inquiry.

Citizens for Responsibility and Ethics in Washington and Public Citizen, nonprofit advocacy groups, sent their own requests to the ethics office to investigate whether Ms. Conway’s comments went over the line. The director of the office, Walter M. Shaub Jr., has said publicly that the president needs to do more to separate himself from his businesses.