Special counsel Robert Mueller worked for firm that represented Ivanka, Kushner and Manafort
Robert Mueller (FBI)

The former FBI director named to oversee the Justice Department's investigation of Trump campaign ties to Russia works at a law firm that represents the president's daughter and two other key campaign figures who have been implicated in the probe.

Robert Mueller, who was named Wednesday as special counsel in the probe, has worked since 2014 at the law firm Wilmer Hale -- which represents Ivanka Trump and her husband, Jared Kushner, as well as former campaign chairman Paul Manafort, reported Politico.

Manafort is under congressional investigation for his business and political dealings in Ukraine on behalf of Kremlin loyalists, and both he and Kushner -- a key adviser during the Trump campaign and transition and now a senior White House adviser -- have agreed to testify before the Senate Intelligence Committee.

Congressional investigators want to question Kushner, the president's son-in-law, about why he failed to disclose his meetings with Russian ambassador Sergey Kislyak and Russian business leaders on his security clearance forms.

The president's daughter also works in the White House.

Richard Painter, the former White House ethics lawyer under President George W. Bush, said government attorneys are usually required to recuse themselves from cases involving clients of their former firms.

But Painter, who has joined a lawsuit accusing Trump of violating the Constitution's Emoluments Clause, said the Justice Department is permitted to waive that requirement.

"I would support them using that authority," Painter told Politico. "It doesn't really make sense for him to oversee one part of the investigation and recuse from others"

"The real risk here is interference by the White House or by [Attorney General Jeff] Sessions' appointees, not some issue involving Wilmer Hale," he added.

The co-managing director of Wilmer Hale told the website that Mueller did not play any part in the firm's work on behalf of Manafort, Trump or Kushner.