Ms Conway's remarks on Thursday drew a sharp and unusual rebuke from a top Republican lawmaker, House Oversight Committee chairman Jason Chaffetz of Utah, who said the comments were "absolutely wrong, wrong, wrong" and "clearly over the line".
Later, she said: "Go buy Ivanka's stuff, is what I would say".
Chaffetz and the committee's ranking minority member, Democrat Elijah Cummings, asked the U.S. Office of Government Ethics in a letter to determine whether disciplinary action should be brought against Conway.
During an interview this morning with Fox & Friends, Kellyanne Conway discussed Nordstorm's decision to drop Ivanka's jewellery and fashion line.
The controversy over Conway came only one day after Trump ripped a store chain on twitter for pulling Ivanka's brand off the shelf, tweeting that his daughter was treated unfairly by the store chain.
Chaffetz told NBC News today Conway's hawking of Ivanka's products crossed a line.
Spicer said Wednesday that Trump was responding to an "attack on his daughter" when he posted the tweet and that "he has every right to stand up for his family and applaud their business activities, their success".
Larry Noble, the general counsel of the Campaign Legal Center, a nonpartisan organization of election law experts, said Trump's tweet was "totally out of line". The large national discount retailers T. J. Maxx and Marshalls, and Neiman Marcus, the luxury department store, for example, have recently taken steps to give less prominence to Ms. Trump's products.
Mr. Trump's complaint also raised questions about how he might handle the moves of numerous other companies as their relationships with Trump brands change.