In a letter to White House deputy counsel Stefan Passantino, OGE director Walter Shaub said the White House failed to discipline Conway despite conduct that may have violated a federal ethics rule prohibiting "using one's official position to endorse any product or service."
Shaub is referring to Conway's February 9 "Fox and Friends" appearance in which she encouraged viewers to "go buy Ivanka's stuff," following the decision by Nordstrom to pull Trump's clothing and accessory brand products from its shelves.
Shaub's letter referred to the incident as a "misuse of position."
Passantino released a letter last week declining to discipline Conway and saying she "acted inadvertently" and had no "nefarious motive or intent to benefit personally."
Shaub said he took issue with the White House's decision, telling Passantino, "not taking disciplinary action against a senior official under such circumstances risks undermining the ethics program."
Shaub said he was even more concerned about a portion of Passantino's letter that questioned whether "many" of OGE rules apply to White House employees.
Shaub takes issue with the claim, saying, "the assertion is incorrect, and the letter cites no legal basis for it."
"Presidential administrations have not considered it appropriate to challenge the applicability of ethics rules to the entire executive branch," Shaub writes. "It is critical to the public's faith in the integrity of government that White House employees be held to the same standard of ethical accountability as other executive branch employees."
In a separate letter responding to Chaffetz and Cummings, Shaub notes that the White House has made its decision not to further discipline Conway and that OGE "cannot impose disciplinary action on an executive branch employee."
The White House and Office of Government Ethics did not respond immediately for requests for follow-up comment on the letter.