Conway, in a Fox News interview from the White House, urged people to "go buy Ivanka's stuff."
"Go buy Ivanka's stuff, is what I would tell you," Conway said. "It's a wonderful line. I own some of it. I fully -- I'm going to just, I'm going to give a free commercial here: Go buy it today, everybody. You can find it online."
The comments could run afoul with federal law that bars public employees from making an "endorsement of any product, service or enterprise, or for the private gain of friends, relatives, or persons with whom the employee is affiliated in a nongovernmental capacity."
The top Democrat on the House Oversight Committee, Rep. Elijah Cummings of Maryland joined with Republican Chairman Jason Chaffetz to refer Conway to the government ethics watchdog office for potentially breaking rules barring government employees from endorsing private businesses.
"We request you review Conway's statements and act primptly on the basis of your findings," the two jointly wrote in a letter to the US Office of Government Ethics.
White House press secretary Sean Spicer said during his daily briefing: "Kellyanne has been counseled. ... She's been counseled on that subject."
The White House counsel's office talked to Conway, not long after her appearance on "Fox & Friends," an official told CNN. The counsel's office informed her that what she said on television was at odds with ethical guidelines. The official said Conway did not push back, acknowledging her misstep.
In an appearance on Fox News Thursday evening, Conway said she spoke with the President and believes he supports her despite the potential ethics violation. She also said she was "aware" of the letter from the oversight committee.
"I spent a lot of time with the President of the United States this afternoon, and he supports me 100%," Conway said.
The incident could spark a broader discussion inside the West Wing about conflicts of interest, the official said. White House counsel Don McGhan is in the process of making sure everyone is clear about rules and the law.
Cummings pointed to the comments, writing to Chaffetz, R-Utah, "this appears to be a textbook violation of government ethics laws and regulations enacted to prevent the abuse of an employee's government position."
The Maryland Democrat cited federal statutes, an executive order signed by President George W. Bush and regulations put out by the Office Government Ethics that prohibit using public office for personal gain.
Cummings argued that since the oversight panel has jurisdiction over laws addressing White House employees it should make the referral.
A spokeswoman for Cummings told CNN that the Maryland Democrat spoke by phone with Chaffetz and that they are drafting a joint letter to the Office of Government Ethics asking what penalty it would recommend for Conway.
In an interview Thursday afternoon with CNN's Jake Tapper, Sen. Cory Booker said, Conway "clearly broke the law."
He tied the incident into a broader criticism of Trump's businesses, which he said remained a major cause for concern and caused the President to violate the Emoluments clause of the Constitution.
Different government agencies have different penalties for rules violations for employees using public office for private gain, with some imposing a five-day suspension to removal, and others recommending a two week suspension to removal for the offense.
It's the latest in a string of ethics concerns raised about the Trump administration's relationship with the family's private businesses since he assumed office.
Spicer did not outline what he meant by Conway being "counseled."
When pressed for details, Spicer simply said: "That's it."