The Office of Government Ethics has asked the White House to look into whether its own ethics lawyer might have violated the administration's conflict of interest rules.

Walter Shaub, the ethics office director, raised the concern in a letter to Democratic lawmakers Thursday.

At issue is whether Stefan Passantino, a White House lawyer who handles ethics issues for the president's staff, ran afoul of the rules because of his relationship with Carl Icahn, a billionaire investor who is an unofficial adviser to President Trump. The White House says he did nothing wrong.

Before he joined the White House, Passantino provided legal services for Icahn's financial firm, according to a financial disclosure form that Passantino signed in January.

The White House's own ethics pledge, issued in an executive order from Trump in January, says that employees must avoid official business involving their former clients for two years.

Shaub is questioning an interview that Passantino gave to Bloomberg News in February which he described Icahn's role as an unofficial adviser to Trump.

Bloomberg News was raising questions about Icahn's role in brokering a proposed change to U.S. biofuels policy. News of that potential change sent the stock of a Texas refining company soaring, and Icahn's stake grew by as much as $126 million. Shaub did not address that matter.

In the article, Passantino said that Icahn "does not have a position with the administration nor a policymaking role."

Related: Senators say Carl Icahn already using Trump role for 'personal gain'

Exactly what role Icahn would play in a Trump administration, official or otherwise, had been an ongoing question. Shaub called it "concerning" that Passantino appeared to be describing the White House's official legal position on Icahn in a media report.

White House spokeswoman Kelly Love has said that Icahn is not a government employee and is "simply a private citizen" whose opinion Trump respects.

Icahn did not immediately respond to a request for comment from CNNMoney on Thursday.

Shaub, in his letter to the Democrats, said he didn't have enough information and was "bringing the matter to the attention of the Counsel to the President for his review and a determination as to whether action is warranted."

Lindsay Walters, a White House spokeswoman, said "no reasonable person" would suggest that Passantino broke the rules simply by relaying the fact that Icahn didn't work for the White House. She also said Passantino has not spoken with Icahn since joining the administration.

She accused Shaub and the Democrats of "distorting facts and attempting to tarnish the White House for purposes of a partisan agenda."

Related: GOP lawmaker raises 'serious questions' about Kushner family conflicts

The relationship between the White House and the Office of Government Ethics has been tense since Trump became president.

They have feuded repeatedly, including over the release of ethics waivers the White House has given its staff.